Fix glance metadata SQL query performance

The query built to retrieve glance metadata associated to a volume
was sub-optimal: all rows of volume_glance_metadata were returned.

Fix it by properly joining the 2 tables with volume_id field.

Closes-bug: #1349936
Change-Id: Ic09414de769e71f8b8f99113838af48d8520e187
Merge "Fix glance metadata SQL query performance"