ktest: Added config_bisect test type

Added the ability to do a config_bisect. It starts with a bad
config and does the following loop.

	Enable half the configs.
	if none of the configs to check are not enabled
	 (caused by missing dependencies) enable the other half.
	Run the test
	if the test passes, remove the configs from the check
	  but enabled them for further tests (to satisfy
	  dependencies).
	else
	  Remove any config that was not enabled, as we have found
	  a new config that can cause a failure.
	loop till we have only one config left.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>