tests: add possibility to disable leak check for single test

In tests that are using external libraries (i. e. pthread) we
can get failure because of leaks in the external library.
Until we have some better solution (if ever), let these (and only these)
tests to disable leak checks.

Signed-off-by: Marek Chalupa <mchqwerty@gmail.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>

tests/test-runner.c

@@ -175,6 +175,8 @@ check_leaks(int supposed_alloc, int supposed_fds)
 				num_fds - supposed_fds);
 			abort();
 		}
+	} else {
+		fprintf(stderr, "Leak checks disabled\n");
 	}
 }