Add carrierconfigs to treat mdn as VM number

Add the carrier configs which specify whether the carrier treats the mdn
as an additional voicemail number.

Change-Id: I9bc095427564cf587734fd2d308a88abc7d88891
Fix: 29145323
Test: build and flash on device
diff --git a/assets/carrier_config_310004.xml b/assets/carrier_config_310004.xml
index db112f8..381797d 100644
--- a/assets/carrier_config_310004.xml
+++ b/assets/carrier_config_310004.xml
@@ -2,6 +2,7 @@
 <carrier_config_list>
     <carrier_config>
         <boolean name="sms_requires_destination_number_conversion_bool" value="true" />
+        <boolean name="mdn_is_additional_voicemail_number_bool" value="true" />
         <boolean name="operator_selection_expand_bool" value="true" />
         <int name="aliasMinChars" value="2" />
         <int name="smsToMmsTextThreshold" value="7" />