Use cached volumes in REST API extensions

This patch caches db volumes in the core volumes API so that they can be
used in the host and tenant attribute API extensions in order to lower
the response time by avoiding costly individual db queries for each
volume in the REST API contributions.

Change-Id: Ie0cbe929379df32fddbdce1953f13b6f26208bff
Partial-Bug: #1197612
Merge "Use cached volumes in REST API extensions"