Fix glance bootstrap with file backend

Change https://review.opendev.org/#/c/670247/ attempted to fix glance
deployment with the file backend. However, it added a new bug by being
more strict about only generating configuration where the container will
be deployed. This means that the current method of running the glance
bootstrap container on any host in glance-api group could be broken,
since it needs the container configuration.

This change only runs the bootstrap container on hosts in the
glance_api_hosts list, which in the case of the file backend typically
only contains one host.

This change also fixes up some logic during rolling upgrade, where we
might not generate new configuration for the bootstrap host.

Change-Id: I83547cd83b06ddefb3a9e1f39844537bdb32bd7f
Related-Bug: #1836151