Deployment of bare metal instances on Ironic fails when using a customized disk layout with LVM

Issue

After creating an image using diskimage-builder and customizing the FS layout to use LVM, system doesn't boot and ironic-conductor.log shows the following traces:

2019-07-09 06:55:18.148 1 INFO ironic.conductor.utils [req-9cac125f-001c-4211-ba5a-b022cb0b34e2 - - - - -] Successfully set node 6b35f375-50c6-450e-bc6e-0bbdde518398 power state to power off by power off.
2019-07-09 06:55:26.202 1 ERROR ironic.drivers.modules.agent_base_vendor [req-9cac125f-001c-4211-ba5a-b022cb0b34e2 - - - - -] Asynchronous exception: Node failed to deploy. Exception: Couldn't determine the UUID of the root partition or the disk identifier after deploying node 6b35f375-50c6-450e-bc6e-0bbdde518398 for node 6b35f375-50c6-450e-bc6e-0bbdde518398: InstanceDeployFailure: Couldn't determine the UUID of the root partition or the disk identifier after deploying node 6b35f375-50c6-450e-bc6e-0bbdde518398
2019-07-09 06:55:26.202 1 ERROR ironic.drivers.modules.agent_base_vendor Traceback (most recent call last):
2019-07-09 06:55:26.202 1 ERROR ironic.drivers.modules.agent_base_vendor   File "/usr/lib/python2.7/site-packages/ironic/drivers/modules/agent_base_vendor.py", line 316, in heartbeat
2019-07-09 06:55:26.202 1 ERROR ironic.drivers.modules.agent_base_vendor     self.continue_deploy(task)
2019-07-09 06:55:26.202 1 ERROR ironic.drivers.modules.agent_base_vendor   File "/usr/lib/python2.7/site-packages/ironic_lib/metrics.py", line 60, in wrapped
2019-07-09 06:55:26.202 1 ERROR ironic.drivers.modules.agent_base_vendor     result = f(*args, **kwargs)
2019-07-09 06:55:26.202 1 ERROR ironic.drivers.modules.agent_base_vendor   File "/usr/lib/python2.7/site-packages/ironic/conductor/task_manager.py", line 148, in wrapper
2019-07-09 06:55:26.202 1 ERROR ironic.drivers.modules.agent_base_vendor     return f(*args, **kwargs)
2019-07-09 06:55:26.202 1 ERROR ironic.drivers.modules.agent_base_vendor   File "/usr/lib/python2.7/site-packages/ironic/drivers/modules/iscsi_deploy.py", line 408, in continue_deploy
2019-07-09 06:55:26.202 1 ERROR ironic.drivers.modules.agent_base_vendor     uuid_dict_returned = do_agent_iscsi_deploy(task, self._client)
2019-07-09 06:55:26.202 1 ERROR ironic.drivers.modules.agent_base_vendor   File "/usr/lib/python2.7/site-packages/ironic_lib/metrics.py", line 60, in wrapped
2019-07-09 06:55:26.202 1 ERROR ironic.drivers.modules.agent_base_vendor     result = f(*args, **kwargs)
2019-07-09 06:55:26.202 1 ERROR ironic.drivers.modules.agent_base_vendor   File "/usr/lib/python2.7/site-packages/ironic/drivers/modules/iscsi_deploy.py", line 333, in do_agent_iscsi_deploy
2019-07-09 06:55:26.202 1 ERROR ironic.drivers.modules.agent_base_vendor     uuid_dict_returned = continue_deploy(task, iqn=iqn, address=address)
2019-07-09 06:55:26.202 1 ERROR ironic.drivers.modules.agent_base_vendor   File "/usr/lib/python2.7/site-packages/ironic_lib/metrics.py", line 60, in wrapped
2019-07-09 06:55:26.202 1 ERROR ironic.drivers.modules.agent_base_vendor     result = f(*args, **kwargs)
2019-07-09 06:55:26.202 1 ERROR ironic.drivers.modules.agent_base_vendor   File "/usr/lib/python2.7/site-packages/ironic/drivers/modules/iscsi_deploy.py", line 278, in continue_deploy
2019-07-09 06:55:26.202 1 ERROR ironic.drivers.modules.agent_base_vendor     _fail_deploy(task, msg)
2019-07-09 06:55:26.202 1 ERROR ironic.drivers.modules.agent_base_vendor   File "/usr/lib/python2.7/site-packages/ironic/drivers/modules/iscsi_deploy.py", line 240, in _fail_deploy
2019-07-09 06:55:26.202 1 ERROR ironic.drivers.modules.agent_base_vendor     raise exception.InstanceDeployFailure(msg)
2019-07-09 06:55:26.202 1 ERROR ironic.drivers.modules.agent_base_vendor InstanceDeployFailure: Couldn't determine the UUID of the root partition or the disk identifier after deploying node 6b35f375-50c6-450e-bc6e-0bbdde518398