btrfs: close_bdev_exclusive() should use the same @flags as the matching open_bdev_exclusive()

In the failure path of __btrfs_open_devices(), close_bdev_exclusive()
is called with @flags which doesn't match the one used during
open_bdev_exclusive().  Fix it.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Chris Mason <chris.mason@oracle.com>

fs/btrfs/volumes.c

@@ -638,7 +638,7 @@ static int __btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
 error_brelse:
 		brelse(bh);
 error_close:
-		close_bdev_exclusive(bdev, FMODE_READ);
+		close_bdev_exclusive(bdev, flags);
 error:
 		continue;
 	}