[Fuchsia] Fix runner scripts to stop test server spawner

Previously the net_unittests was not stopping test server spawner as
expected.
This change should help debug the linked bug: now if a test server is
not stopped by one of the tests it will be reported by the
SpawningServer.Stop() in the log.

Bug: 913156
Change-Id: If4ad371f4a03b4f44ca4f8cb51b2c8a2a328f647
Reviewed-on: https://chromium-review.googlesource.com/c/1387810Reviewed-by: Fabrice de Gans-Riberi <fdegans@chromium.org>
Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#618410}

build/fuchsia/test_runner.py

@@ -106,7 +106,7 @@ def main():
       target.PutFile(args.test_launcher_filter_file, TEST_FILTER_PATH)
       child_args.append('--test-launcher-filter-file=' + TEST_FILTER_PATH)
 
-    forwarder = None
+    test_server = None
     if args.enable_test_server:
       test_server = SetupTestServer(target, test_concurrency)
 
@@ -115,9 +115,8 @@ def main():
         args.output_directory, target, args.package, args.package_name,
         args.package_dep, child_args, run_package_args)
 
-    if forwarder:
-      forwarder.terminate()
-      forwarder.wait()
+    if test_server:
+      test_server.Stop()
 
     if args.test_launcher_summary_output:
       target.GetFile(TEST_RESULT_PATH, args.test_launcher_summary_output)