tests: use igt_fail instead of exit(param != 0)

Mostly a sed job with too manual fixups:
- one case of using _exit instead of exit
- and one case which under some conditions use 77, so convert that
  check to an igt_skip.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

tests/gem_ctx_basic.c

@@ -162,7 +162,7 @@ int main(int argc, char *argv[])
 		ret = pthread_join(threads[i], &retval);
 		thread_status = *(int *)retval;
 		if (!ret && thread_status)
-			exit(thread_status);
+			igt_fail(thread_status);
 	}
 
 	free(returns);