MDEV-22757 Assertion !binlog || exist_hton_without_prepare' failed in MYSQL_BIN_LOG::unlog_xa_prepare

The assert fired falsely having not captured two more not apparent
possiblities in its condition.

They are masked out hton error out of REPLACE execution (so at later xa-prepare
that engine is still present as read-write) and a prepare-capable engine
which also may not be an actual participant in the xa transation. That
engine, such as SEQUENCE, though does create its own event block.