Support multiple xml_config files in ServoTest class.

By changing the args xml_config in Servo to be a list.

BUG=chromium-os:19710,chrome-os-partner:5966
TEST=run_remote_tests.sh --remote=$REMOTE_IP -a \
     "xml_config=servo_x86-alex_overlay.xml servo_vid=0x18d1 servo_pid=0x5001" \
     firmware_DevMode

Change-Id: I0b62953b8c55e6972c27452720d7f2f34ab6397a
Reviewed-on: https://gerrit.chromium.org/gerrit/11114
Reviewed-by: Todd Broch <tbroch@chromium.org>
Commit-Ready: Tom Wai-Hong Tam <waihong@chromium.org>
Tested-by: Tom Wai-Hong Tam <waihong@chromium.org>
diff --git a/server/cros/servo_test.py b/server/cros/servo_test.py
index 95108d5..e29a5ee 100644
--- a/server/cros/servo_test.py
+++ b/server/cros/servo_test.py
@@ -84,7 +84,7 @@
         # Assign default arguments for servo invocation.
         args = {
             'servo_host': 'localhost', 'servo_port': 9999,
-            'xml_config': 'servo.xml', 'servo_vid': None, 'servo_pid': None,
+            'xml_config': ['servo.xml'], 'servo_vid': None, 'servo_pid': None,
             'servo_serial': None, 'use_pyauto': False}
 
         # Parse arguments from AFE and override servo defaults above.
@@ -97,7 +97,13 @@
         for arg in cmdline_args:
             match = re.search("^(\w+)=(.+)", arg)
             if match:
-                args[match.group(1)] = match.group(2)
+                key = match.group(1)
+                val = match.group(2)
+                # Support multiple xml_config by appending it to a list.
+                if key == 'xml_config':
+                    args[key].append(val)
+                else:
+                    args[key] = val
 
         # Initialize servotest args.
         self._client = host;