Clear the network service disk cache for each apptest run.

R=qsr@chromium.org

Review URL: https://codereview.chromium.org/1384773003 .

Cr-Mirrored-From: https://github.com/domokit/mojo
Cr-Mirrored-Commit: 18baf5b6673402d39179c0bdcd726df80e1f328d

mojo_test

diff --git a/mojo_test b/mojo_test
index 8f06f42..f3fa0d0 100755
--- a/mojo_test
+++ b/mojo_test
@@ -50,6 +50,7 @@
 _logger = logging.getLogger()
 
 _CACHE_SERVICE_URL = 'mojo:url_response_disk_cache'
+_NETWORK_SERVICE_URL = 'mojo:network_service'
 
 
 def main():
@@ -68,9 +69,11 @@
       # We need root to have the stdout of the shell available on the host.
       config.require_root = True
     shell, common_shell_args = shell_arguments.get_shell(config, shell_args)
-    # Tests must be reproducible. Start with an empty cache.
+    # Tests must be reproducible, start with empty caches.
     common_shell_args.append(
         "--args-for=%s %s" % (_CACHE_SERVICE_URL, "--clear"))
+    common_shell_args.append(
+        "--args-for=%s %s" % (_NETWORK_SERVICE_URL, "--clear"))
   except shell_config.ShellConfigurationException as e:
     print e
     return 1