rbd/glance/keyring: fix wrong collected resource

In the commit 8e537e4b50bdfbc87a5914baca4e93c45ddce918, a wrong resource
collection has been introduced which can make fail the situation when
Glance API & Cinder Volume are not on the same nodes.

For Glance, the resource collected was the Cinder keyring instead of
Glance keyring.
This patch fix this regression introduced on 4th march.

Signed-off-by: Emilien Macchi <emilien.macchi@enovance.com>
Merge pull request #596 from enovance/glance_ceph_keyring

rbd/glance/keyring: fix wrong collected resource