mdmon: pass symbolic name to mdmon instead of device name.

mdmon: pass symbolic name to mdmon instead of device name.

Now that names in /dev are usually created (eventually) by udev,
it isn't really safe to rely in finding a name in /dev to pass to
mdmon to identify which array to monitor.
And it isn't really necessary to have a name in /dev.
So just pass the symbolic name, e.g. md127 or md123.

Change util.c to pass that name, and change mdmon to process the
name sensibly.

Signed-off-by: NeilBrown <neilb@suse.de>