Monitor: don't get confused if utime is never set.

externally managed arrays do not (currently) cause utime in
GET_ARRAY_INFO to be updated.  So if it is zero, just assume the
current time.
This will cause GET_DISK_INFO to be called more often, but as we do
the scan only every 60 seconds normally, a few extra syscalls isn't
going to make a big difference.

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

Monitor.c

@@ -284,6 +284,10 @@ int Monitor(mddev_dev_t devlist,
 					mse = mse2;
 				}
 
+			if (array.utime == 0)
+				/* external arrays don't update utime */
+				array.utime = time(0);
+
 			if (st->utime == array.utime &&
 			    st->failed == array.failed_disks &&
 			    st->working == array.working_disks &&