IMS: Handle connection event to enable merge button

When conferece request fails, connection event with merge failed
event will be posted. This need to be handled to update the call UI.

Change-Id: Ib202b490c5c60d4d842d1cdf08e3c3b8aec3aab8
CRs-Fixed: 1099503
diff --git a/InCallUI/src/com/android/incallui/Call.java b/InCallUI/src/com/android/incallui/Call.java
index 60bc42e..aea2003 100644
--- a/InCallUI/src/com/android/incallui/Call.java
+++ b/InCallUI/src/com/android/incallui/Call.java
@@ -366,6 +366,12 @@
                     List<android.telecom.Call> conferenceableCalls) {
                 update();
             }
+
+            @Override
+            public void onConnectionEvent(android.telecom.Call call, String event, Bundle extras) {
+                Log.d(this, "TelecomCallCallback onConnectionEvent call=" + call);
+                update();
+            }
     };
 
     boolean mIsActiveSub = false;