[Intel-gfx] [PATCH i-g-t 3/3] intel_gvtg_test: Handle system(3) return value.

[Chris Wilson]

Quoting Tvrtko Ursulin (2017-11-03 11:47:56)
> From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> 
> Avoid the build warning by checking the pkill either did not find
> any guests or managed to send a signal to all of them.

This is tools, do we have the igt framework so that calling igt_assert
when lead to a confusing mass of "not in a test" warnings?
-Chris