btrfs: fix fscrypt name leak after failure to join log transaction

When logging a new name, we don't expect to fail joining a log transaction
since we know at least one of the inodes was logged before in the current
transaction. However if we fail for some unexpected reason, we end up not
freeing the fscrypt name we previously allocated. So fix that by freeing
the name in case we failed to join a log transaction.

Fixes: ab3c5c18 ("btrfs: setup qstr from dentrys using fscrypt helper")
Reviewed-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>