From OSP12 the Ceph upgrade is triggered when StackUpdateType is set to UPGRADE but in OSP13 we don't set that parameter anymore.
For ceph-ansible we need to discern when an upgrade is happening to swith to the appropriate playbook.
We only want to run the workflows during the -converge step so setting and unsetting StackUpdateType is not possible anymore (-converge is the last step of the upgrade process)
The templates for ceph-ansible used to point it to a specific playbook when upgrade was necessary. 
I think a potential fix/workaround which we can experiment with is in 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.