Follows existing backends patterns to add support for the GlusterFS
NFS driver.
NFS server type used by the GlusterFS backend, Gluster or Ganesha,
currently supports Gluster.
The GlusterFS NFS driver needs to install the glusterfs-fuse package
in the kolla images manila share container in advance, which has been merged
in https://review.opendev.org/747510

Change-Id: I7fdb121b5bf9850d62246a24f9b17d226028c2ca