[leaksrunner] Use pool.map_async.get(999999) instead of pool.map so that we support C-c.

Author: gottesmm

benchmark/scripts/perf_test_driver/perf_test_driver.py

@@ -99,7 +99,7 @@ def prepare_input_wrapper(name):
         if self.enable_parallel:
             p = multiprocessing.Pool()
             z = zip([self] * len(prepared_input), prepared_input)
-            results = p.map(_unwrap_self, z)
+            results = p.map_async(_unwrap_self, z).get(999999)
         else:
             results = map(self.process_input, prepared_input)