Temp fix for handoff on CDMA

With this CL we no longer disconnect the WiFi call when doing
a handoff from WiFi to to CDMA. Since CDMA becomes active
quickly, disconnecting the WiFi call will end the call and stop
handoff.

This is a temp fix. I'll implement a proper fix when we switch
to daisy chaining.

Bug: 15019557
Change-Id: I6e5d21bafd41948c8bd429740e36f31ab81deadc
diff --git a/src/com/android/telecomm/CallsManager.java b/src/com/android/telecomm/CallsManager.java
index b21be69..bfeea49 100644
--- a/src/com/android/telecomm/CallsManager.java
+++ b/src/com/android/telecomm/CallsManager.java
@@ -605,8 +605,9 @@
         handoffCall.removeListener(this);
 
         if (wasSuccessful) {
-            // Disconnect.
-            originalCall.disconnect();
+            if (TelephonyUtil.isCurrentlyPSTNCall(originalCall)) {
+                originalCall.disconnect();
+            }
 
             // Synchronize.
             originalCall.setCallService(handoffCall.getCallService(), handoffCall);