Initialize RBD pool

When we deploy devstack, we need to initialize the RBD pool.

Not doing so means that functionality like rbd trash purge
scheduling will not work correctly.

Ref: https://docs.ceph.com/en/latest/start/quick-rbd/
Change-Id: I5b0b3b83fb7ef805929fdcd106a5c8a988b05ec4

devstack/lib/ceph

@@ -879,6 +879,8 @@ function configure_ceph_cinder {
 
     sudo chown ${STACK_USER}:$(id -g -n $whoami) \
         ${CEPH_CONF_DIR}/ceph.client.${CINDER_CEPH_USER}.keyring
+
+    sudo rbd pool init ${CINDER_CEPH_POOL}
 }
 
 # install_ceph() - Collect source and prepare