[Train] Fix Tacker config for the local Glance store

It turned out the previous fix ([1]) was incomplete.
Additionally, it seems we have to limit Tacker server
to one instance co-located with conductor.

[1] https://review.opendev.org/684275
commit b96ade3c

Change-Id: I9ce27d5f68f32ef59e245960e23336ae5c5db905
Closes-bug: #1853715
Related-bug: #1845142