[moblab] Provide default for getting the test args from config.

If a user AU's and does not go through the config wizard again
the wifi test args are missing from the config.

Provide a default value in the get request.

BUG=chromium:752558
TEST=unit tests and locally on moblab.

Change-Id: If1904a289df8effd54b62158f7310a17c0a6fe09
Reviewed-on: https://chromium-review.googlesource.com/602677
Commit-Ready: Keith Haddow <haddowk@chromium.org>
Tested-by: Keith Haddow <haddowk@chromium.org>
Reviewed-by: Keith Haddow <haddowk@chromium.org>
Reviewed-by: Michael Tang <ntang@chromium.org>
(cherry picked from commit b940817305207a493402e72b05601aad0038e8ee)
Reviewed-on: https://chromium-review.googlesource.com/603129
Commit-Queue: Keith Haddow <haddowk@chromium.org>
diff --git a/frontend/afe/moblab_rpc_interface.py b/frontend/afe/moblab_rpc_interface.py
index 8e09b6d..299a93f 100644
--- a/frontend/afe/moblab_rpc_interface.py
+++ b/frontend/afe/moblab_rpc_interface.py
@@ -803,14 +803,13 @@
     else:
         list_suite_args = None
 
-    test_args = {'ssid': None, 'wifipass': None}
+    test_args = {}
 
-    ap_name =_CONFIG.get_config_value('MOBLAB', _WIFI_AP_NAME)
-    if ap_name and ap_name != 'None':
-      test_args['ssid'] = ap_name
-    ap_pass =_CONFIG.get_config_value('MOBLAB', _WIFI_AP_PASS)
-    if ap_pass and ap_pass != 'None':
-      test_args['wifipass'] = ap_pass
+    ap_name =_CONFIG.get_config_value('MOBLAB', _WIFI_AP_NAME, default=None)
+    test_args['ssid'] = ap_name
+    ap_pass =_CONFIG.get_config_value('MOBLAB', _WIFI_AP_PASS, default=None)
+    test_args['wifipass'] = ap_pass
+
     afe = frontend.AFE(user='moblab')
     afe.run('create_suite_job', board=board, builds=builds, name=suite,
     pool=pool, run_prod_code=False, test_source_build=build,