rbd: don't use /dev/rbd/pool/image; use sysfs to find rbd device instead

rbd: if rbd image is not formatted, format it to the designated filesystem type

rbd: update example README.md and include instructions to get base64 encoded Ceph secret

if rbd fails to lock image, unmap the image before exiting

Signed-off-by: Huamin Chen <hchen@redhat.com>

pkg/volume/rbd/rbd.go

@@ -131,7 +131,7 @@ func (plugin *rbdPlugin) newBuilderInternal(spec *volume.Spec, podUID types.UID,
 			Pool:     pool,
 			ReadOnly: readOnly,
 			manager:  manager,
-			mounter:  mounter,
+			mounter:  &mount.SafeFormatAndMount{mounter, exec.New()},
 			plugin:   plugin,
 		},
 		Mon:     source.CephMonitors,