Rename disable add call extra

Used to be DISABLE_ADD_CALL_DURING_VIDEO_CALL, now just
DISABLE_ADD_CALL. The meaning has also changed -- having the extra set
means that adding calls should be disabled no matter what.

Bug: 29047863
Change-Id: Icd8966492b264a9c64dc4880080a706032f0759c
diff --git a/telephony/java/android/telephony/CarrierConfigManager.java b/telephony/java/android/telephony/CarrierConfigManager.java
index a5e50aa..9603662 100644
--- a/telephony/java/android/telephony/CarrierConfigManager.java
+++ b/telephony/java/android/telephony/CarrierConfigManager.java
@@ -819,7 +819,9 @@
             "allow_merge_wifi_calls_when_vowifi_off_bool";
 
     /**
-     * When true, indicates that adding a call is disabled when there is an ongoing video call.
+     * When true, indicates that adding a call is disabled when there is an ongoing video call
+     * or when there is an ongoing call on wifi which was downgraded from video and VoWifi is
+     * turned off.
      */
     public static final String KEY_ALLOW_ADD_CALL_DURING_VIDEO_CALL_BOOL =
             "allow_add_call_during_video_call";