os/bluestore: fix _extend_log seq advance
when extending the log, the sequence was left on a bad state because it would first create a transaction to update with the current seq number but leave the "real" transaction with the same sequence number which should be `extend_log_transaction.seq + 1`.
Signed-off-by: Pere Diaz Bou <pdiabou@redhat.com>
Fixes: https://tracker.ceph.com/issues/71199
(cherry picked from commit
0210f57a5ec8a8c0ea76a72984f39dae24986cb0)
(cherry picked from commit
b76623504a544feba2adf7a196ddbd59d1b8b8f4)