policy: support devices with multiple paths.

policy: support devices with multiple paths.

As new releases of Linux some time change the name of
a path, some distros keep "legacy" names as well.  This
is useful, but confuses mdadm which assumes each device has
precisely one path.

So change this assumption:  allow a disk to have several
paths, and allow any to match when looking for a policy
which matches a disk.

Reported-and-tested-by: Mariusz Tkaczyk <mariusz.tkaczyk@intel.com>
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Jes Sorensen <jsorensen@fb.com>