If we early exit here, 'handle' needs to be freed, or some memory leaks.

Fixes: ed5cc702 ("block: Add config option to not allow writing to mounted devices")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/8eaec334781e695810aaa383b55de00ca4ab1352.1703439383.git.christophe.jaillet@wanadoo.frReviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Christian Brauner <brauner@kernel.org>