Analysis: There is race between drop table and encryption threads that
could cause encryption thread to enter mutex that has been already
released.

Fix: When destroying crypt_data first enter the mutex and set crypt data
unavailable, then release the memory and clean up the data. This should
make the race more unprobable. Additionally, added big_test for
create_or_replace as it could fail testcase timeout
if you have slow I/O (tested that testcase passes with --mem).