Fix DM_MULTIPATH_DEVICE_PATH check in mdadm.rules (#1628192)
    
    This value can be explicitly set to 0 (meaning 'not a multipath
    device'). The check as currently written will match on this, as
    it just matches absolutely any one or more characters at all,
    including 0. Fix the check to only look for '1', the value that
    indicates the device is multipath. This is the same as how
    68-del-part-nodes.rules and 69-dm-lvm-metad.rules do it.
    
    Resolves: bz1628192
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>