Previously, the sql_connection config was overridden for the
glance-registry.conf only, whereas in the glance-api.conf this
is left to default to a non-existent sqlite DB.
This causes an issue with the v2 API is used - in this case,
the glance-api service accesses the DB directly instead of
delegating to the registry service. Since the sqlite DB is
non-existent, such v2 API calls fail with 500 ServerError.
This is especially problematic with cinder, as it tries the
glance v2 API by default when creating a bootable volume from
an image, see:
https://bugzilla.redhat.com/888241
b08af59f34