mdcheck: don't git error if not /dev/md?* devices exist.

If there are no such devices, the 'for' will set '$dev' to
'/dev/md?*', which should be ignored.

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

misc/mdcheck

@@ -77,6 +77,7 @@ find /var/lib/mdcheck -name "MD_UUID*" -type f -mtime +180 -exec rm {} \;
 cnt=0
 for dev in /dev/md?*
 do
+	[ -e "$dev" ] || continue
 	sys=`sysname $dev`
 	if [ ! -f "$sys/md/sync_action" ]
 	then # cannot check this array