Previously the regext expected MOVE_MOUNT_[FT]_*, but in the next patch
a flag that doesn't match that expression will be added, MOVE_MOUNT_SET_GROUP

To make this more future proof, take advantage of the fact that the only
one we don't need to cover is MOVE_MOUNT__MASK and use MOVE_MOUNT_[^_]+_*_.
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>