Capsule upgrade fails due to unable to refresh its features

Issue

• Capsule upgrade fails with errors:

ERROR 2020-11-19T20:44:52 main]  /Stage[main]/Foreman_proxy::Register/Foreman_smartproxy[capsule.example.com]/features: change from ["Ansible", "Discovery", "Dynflow", "Logs", "Pulp Node", "Puppet", "Puppet CA", "SSH", "TFTP", "Templates"] to ["Ansible", "Dynflow", "HTTPBoot", "Logs", "Puppet", "Puppet CA", "TFTP", "Templates"] failed: Proxy capsule.example.com cannot be refreshed: unknown error (response 500)
[ERROR 2020-11-19T20:44:52 main]  /Stage[main]/Foreman_proxy::Register/Foreman_smartproxy[capsule.example.com]: Failed to call refresh: Proxy capsule.example.com cannot be refreshed: unknown error (response 500)
[ERROR 2020-11-19T20:44:52 main]  /Stage[main]/Foreman_proxy::Register/Foreman_smartproxy[capsule.example.com]: Proxy capsule.example.com cannot be refreshed: unknown error (response 500)