The current openstack-glance package ships both, glance-api and glance-registry. In order to better support distributed deployments, this package should be split in 2 packages, one for each service. Please, refer to this thread for the upstream discussion. https://www.redhat.com/archives/rdo-list/2015-March/msg00146.html
Fixed in Delorean: https://review.gerrithub.io/#/c/229724/
Making this packaging change (in Delorean) can break end users quite badly. Is there any benefit to it other than the fact that it would prevent an extra systemd script for one of the Glance servers getting installed (but not used). In other words would installing glance-registry or glance-api in isolation result in less dependencies getting installed if we do this split? If not then I'm not sure this is worth it... and even then maybe it isn't worth breaking end users to save a dependency or two.
Reverted in https://review.gerrithub.io/230453
Setting needinfo for comment 2
Updating the bug with the discussion we had over email. I believe the conclusion is that we'll try to make this change in a way were deployments are not broken by it. If we can't find such solution, we'll probably go ahead and do it anyway. I believe this is is something we should do. The package splitting goes beyond just saving some dependencies. It helps making deployments of Glance semantically correct, if you will.
This bug is against a Version which has reached End of Life. If it's still present in supported release (http://releases.openstack.org), please update Version and reopen.