OPTIMIZE TABLE

OPTIMIZE TABLE for InnoDB tables is handled as recreate + analyze.
The triggered assert checked that an error had been reported if either
recreate or analyze failed. However the assert failed to take into
account that they could have failed because OPTIMIZE TABLE had been
victim of KILL QUERY, KILL CONNECTION or server shutdown.

This patch adjusts the assert to take this possibility into account.
The problem was only noticeable on debug versions of the server.

Test case added to innodb_mysql_sync.test.