Bug #41173 rpl_packet fails sporadically on pushbuild: query 'DROP TABLE t1' failed


The both issues appeared to be a race between the SQL thread executing CREATE table t1
and the IO thread that is expected to stop at the consequent big size event.
The two events need serialization which is implemented.
The early bug required back-porting a part fixes for bug#38350 exclusively for 5.0 version.