Assemble: avoid infinite loop when auto-assembling partial container.

When auto-assembling we loop until we get no successes.

If a device is found that look like it is part of an already-existing
container, but we subsequently fail to add that device, then the fact
that the container is running looks like a success.  This can result
in infinite looping.
So if a container was already partially assemble, and is still only
partially assembled after we try to add devices, then don't treat that
as success.

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

Assemble.c

@@ -990,6 +990,10 @@ static int start_array(int mdfd,
 		}
 		st->ss->free_super(st);
 		sysfs_uevent(content, "change");
+		if (err_ok && okcnt < (unsigned)content->array.raid_disks)
+			/* Was partial, is still partial, so signal an error
+			 * to ensure we don't retry */
+			return 1;
 		return 0;
 	}