ovsdb-idl: Fix expected condition seqno when changes are pending.

ovsdb-idl: Fix expected condition seqno when changes are pending.

Commit 17f22fe46142 tried to address this but only covered some of the
cases.

The correct way to report the expected seqno is to take into account if
there already is a condition change that was requested to the server but
not acked yet.  In that case, the new condition change request will be
sent only after the already requested one is acked.  That is, expected
condition seqno when conditions are up to date is db->cond_seqno + 2 in
this case.

Fixes: 17f22fe46142 ("ovsdb-idl: Return correct seqno from ovsdb_idl_db_set_condition().")
Suggested-by: Ilya Maximets <i.maximets@ovn.org>
Signed-off-by: Dumitru Ceara <dceara@redhat.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>