Enable showing multiple locations for ceph plugin

Currently glance v2 doesn't allow to specify custom
locations for image by default, it returns 403.
To enable this 'show_multiple_locations' param must
be set to True.

When Nova is doing snapshots with Ceph it provides
location to activate image, which fails when we use
Glance v2.

To fix it we change the default param to True.
'show_image_direct_url' will be overridden.

Related to blueprint use-glance-v2-api

Change-Id: Id0f1c398b8b48f2ffc2488b29bc7cbd279069337

devstack/lib/ceph

@@ -470,7 +470,7 @@ sudo tee ${CEPH_CONF_DIR}/ceph.client.${GLANCE_CEPH_USER}.keyring
 sudo chown ${STACK_USER}:$(id -g -n $whoami) \
 ${CEPH_CONF_DIR}/ceph.client.${GLANCE_CEPH_USER}.keyring
 
-iniset $GLANCE_API_CONF DEFAULT show_image_direct_url True
+iniset $GLANCE_API_CONF DEFAULT show_multiple_locations True
 iniset $GLANCE_API_CONF glance_store default_store rbd
 iniset $GLANCE_API_CONF glance_store stores "file, http, rbd"
 iniset $GLANCE_API_CONF glance_store rbd_store_ceph_conf $CEPH_CONF_FILE