An additional warning saying "tc-log cannot be enabled"
is emitted when InnoDB is installed at runtime on mysqld
built with wsrep-patch (-DWITH_WSREP=ON).
This happens because, installing InnoDB increments the
total number of 2pc-capable engines and with wsrep-patch
already enabled - the total count goes >1. Even though,
this condition is sufficient to enable tc-logging, it is
not permitted at runtime, and thus the warning.
Updated the testcase to avoid the warning.
Analysis: At check_trx_exists function InnoDB allocates
a new trx if no trx is found from thd but this newly
allocated trx is not registered to thd. This is unsafe,
because nothing prevents InnoDB plugin from being uninstalled
while there's active transaction. This can cause crashes, hang
and any other odd behavior. It may also corrupt stack, as
functions pointers are not available after dlclose.
Fix: The fix is to use thd_set_ha_data() when
manipulating per-connection handler data. It does appropriate
plugin locking.
