Add a default MMS UA

The default user-agent isn't set, which makes
TelephonyManager.getMmsUserAgent() return an empty string when a
device doesn't have one in its own overlays. Every hardware should
set its own unique name for this, but add a default value for cases
in which is is forgotten.

Fixes android.telephony.cts.TelephonyManagerTest#testTelephonyManager

Change-Id: I8a648014873319ea0d0f1089495d6777b8a1b8bf
diff --git a/overlay/common/frameworks/base/core/res/res/values/config.xml b/overlay/common/frameworks/base/core/res/res/values/config.xml
index 126d435..2d10745 100644
--- a/overlay/common/frameworks/base/core/res/res/values/config.xml
+++ b/overlay/common/frameworks/base/core/res/res/values/config.xml
@@ -30,4 +30,6 @@
         <item>com.google.android.gsf/com.google.android.gsf.update.SystemUpdateService</item>
         <item>com.google.android.gsf/com.google.android.gsf.update.SystemUpdateService$Receiver</item>
     </string-array>
+
+    <string name="config_mms_user_agent">CyanogenMod</string>
 </resources>