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.