Fast forward upgrade from OSP 10 to OSP 13 fails with "Duplicate declaration: (...) is already declared in file (...)" in Red Hat OpenStack Platform

Issue

Fast forward upgrade from OSP 10 to OSP 13 fails with Duplicate declaration: (...) is already declared in file (...) in Red Hat OpenStack Platform.

For example, in a specific deployment, one might see this in the output of openstack overcloud upgrade run --nodes Controller --skip-tags validation:

(...)
        "2019-05-14 23:10:10,720 ERROR: 69217 -- Failed running docker-puppet.py for ceilometer", 
        "2019-05-14 23:10:10,720 ERROR: 69217 -- Notice: hiera(): Cannot load backend module_data: cannot load such file -- hiera/backend/module_data_backend", 
        "2019-05-14 23:10:10,720 ERROR: 69217 -- + mkdir -p /etc/puppet", 
        "+ '[' -n file,file_line,concat,augeas,cron,ceilometer_config,ceilometer_config ']'", 
        "+ TAGS='--tags file,file_line,concat,augeas,cron,ceilometer_config,ceilometer_config'", 
        "+ origin_of_time=/var/lib/config-data/ceilometer.origin_of_time", 
        "+ touch /var/lib/config-data/ceilometer.origin_of_time", 
        "+ /usr/bin/puppet apply --summarize --detailed-exitcodes --color=false --logdest syslog --logdest console --modulepath=/etc/puppet/modules:/usr/share/openstack-puppet/modules --tags file,file_line,concat,augeas,cron,ceilometer_config,ceilometer_config /etc/config.pp", 
        "Warning: ModuleLoader: module 'ceilometer' has unresolved dependencies - it will only see those that are resolved. Use 'puppet module list --tree' to see information about modules", 
        "                    with Stdlib::Compat::String. There is further documentation for validate_legacy function in the README. at [\"/etc/puppet/modules/ceilometer/manifests/init.pp\", 346]:[\"/etc/puppet/modules/tripleo/manifests/profile/base/ceilometer/agent/polling.pp\", 57]", 
        "Warning: Scope(Class[Ceilometer]): ceilometer::rabbit_host, ceilometer::rabbit_hosts, ceilometer::rabbit_password, ceilometer::rabbit_port, ceilometer::rabbit_userid, ceilometer::rabbit_virtual_host and ceilometer::rpc_backend are deprecated. Please use ceilometer::default_transport_url instead.", 
        "                    with Stdlib::Compat::Array. There is further documentation for validate_legacy function in the README. at [\"/etc/puppet/modules/ceilometer/manifests/agent/notification.pp\", 129]:[\"/etc/puppet/modules/tripleo/manifests/profile/base/ceilometer/agent/polling.pp\", 57]", 
        "                    with Stdlib::Compat::Hash. There is further documentation for validate_legacy function in the README. at [\"/etc/puppet/modules/ceilometer/manifests/config.pp\", 35]:[\"/etc/puppet/modules/tripleo/manifests/profile/base/ceilometer.pp\", 148]", 
        "Error: Evaluation Error: Error while evaluating a Resource Statement, Evaluation Error: Error while evaluating a Function Call, Duplicate declaration: Ceilometer_config[oslo_messaging_rabbit/rabbit_qos_prefetch_count] is already declared in file /etc/puppet/modules/ceilometer/manifests/config.pp:38; cannot redeclare at /etc/puppet/modules/oslo/manifests/messaging/rabbit.pp:242 at /etc/puppet/modules/oslo/manifests/messaging/rabbit.pp:242:3  at /etc/puppet/modules/ceilometer/manifests/init.pp:409 on node overcloud-controller-1.localdomain", 
        "2019-05-14 23:10:10,720 INFO: 69217 -- Finished processing puppet configs for ceilometer", 
(...)

grep -i 'is already declared' ffwd-upgrade-run-Controller-output-1.txt
(...)
        "Error: Evaluation Error: Error while evaluating a Resource Statement, Evaluation Error: Error while evaluating a Function Call, Duplicate declaration: Ceilometer_config[oslo_messaging_rabbit/rabbit_qos_prefetch_count] is already declared in file /etc/puppet/modules/ceilometer/manifests/config.pp:38; cannot redeclare at /etc/puppet/modules/oslo/manifests/messaging/rabbit.pp:242 at /etc/puppet/modules/oslo/manifests/messaging/rabbit.pp:242:3  at /etc/puppet/modules/ceilometer/manifests/init.pp:409 on node overcloud-controller-2.localdomain", 
        "Error: Evaluation Error: Error while evaluating a Resource Statement, Evaluation Error: Error while evaluating a Function Call, Duplicate declaration: Ceilometer_config[oslo_messaging_rabbit/rabbit_qos_prefetch_count] is already declared in file /etc/puppet/modules/ceilometer/manifests/config.pp:38; cannot redeclare at /etc/puppet/modules/oslo/manifests/messaging/rabbit.pp:242 at /etc/puppet/modules/oslo/manifests/messaging/rabbit.pp:242:3  at /etc/puppet/modules/ceilometer/manifests/init.pp:409 on node overcloud-controller-0.localdomain", 
        "Error: Evaluation Error: Error while evaluating a Resource Statement, Evaluation Error: Error while evaluating a Function Call, Duplicate declaration: Ceilometer_config[oslo_messaging_rabbit/rabbit_qos_prefetch_count] is already declared in file /etc/puppet/modules/ceilometer/manifests/config.pp:38; cannot redeclare at /etc/puppet/modules/oslo/manifests/messaging/rabbit.pp:242 at /etc/puppet/modules/oslo/manifests/messaging/rabbit.pp:242:3  at /etc/puppet/modules/ceilometer/manifests/init.pp:409 on node overcloud-controller-1.localdomain",