Fix volume_glance_metadata deletion

If volume_glance_metadata does not exist for a certain volume,
it returns an exception and does not delete volume from db.
Avoid deleting it if it does not exist.

Bug: 1209367
Change-Id: Ia607ec5ecfc115c1a593f14236ee93158938a8da
Use a new rest client for every Coraid ESM command

It's workaround for the session corruption bug
in the ESM Appliance.

fix bug #1214433

Change-Id: Ie844f3c95675c4d734390c23ed2d421c159ce8a7
Merge "Use a new rest client for every Coraid ESM command"
Merge "Fix volume_glance_metadata deletion"