Avoid to create executable scripts in MTR var directory, when using
--mem, /dev/shm will used, which might be mounted with noexec flag.

Convert test using GNU touch to pure perl, making test more portable.

Some platforms output Filename (not File name) in error message, add
regex to handle this difference.

Not executing srv_session_deinit_thread() in test_sql_errors.cc ends
in crash, add call.