selftests/resctrl: Add cleanup function to test framework

selftests/resctrl: Add cleanup function to test framework

Resctrl selftests use very similar functions to cleanup after
themselves. This creates a lot of code duplication. Also not being
hooked to the test framework means that ctrl-c handler isn't aware of
what test is currently running and executes all cleanups even though
only one is needed.

Add a function pointer to the resctrl_test struct and attach to it
cleanup functions from individual tests.

Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>