Increase test coverage for cinder.utils

Add new tests for:
        check_ssh_injection()
        create_channel()

Change-Id: I0349d87023567b16d6600f5b38fd1daff5cbbdc8
Fix errors in volume usage audit script

The snapshot_get_active_by_window DB query was returning snapshots
where we couldn't access the related volume object. This was due to
a) the volume not been loaded and the join failing due to detached
session object.
and b) the related volume was deleted so it didn't show return from
the join

Fixes bug: 1220140

Change-Id: I0de993ba0ca482fa9ab80d4d5cdb0ff5cc8e4d7a
Merge "Increase test coverage for cinder.utils"
Merge "Fix errors in volume usage audit script"