WHERE POSSIBLE

Description:
============
mysql-test-run.pl (MTR) has a configuration file mysql-test/include/default_mysqld.cnf
which sets values for various server variables. Some of them maybe needed to run tests
with limited resources available on PB2, while some others maybe there due to legacy
reasons that are not valid anymore.

The settings made by MTR were evaluated to assess whether they were needed. Then,
the setting of variables to non-server-default values were removed from default_mysqld.cnf.
The tests run by MTR were modified or recorded accordingly.

Reviewed-by: Anitha Gopi <anitha.gopi@oracle.com>
Reviewed-by: Sayantan Dutta <sayantan.dutta@oracle.com>
Reviewed-by: Parveez Baig <parveez.baig@oracle.com>
RB: 11707