Finalize MEP functionality.

1) Finish plumbing of PULLING_CALL state.
2) Add new disconnect cause used when maximum number of calls across
all devices has been reached.
3) Add PII mask for toString of ImsExternalCallState.

Bug: 29522023
Change-Id: I78a0a9f3c3d846cfc58a1c5bcc6f105027602cbc

telecomm/java/android/telecom/RemoteConnectionService.java

@@ -117,6 +117,12 @@ final class RemoteConnectionService {
                     .setState(Connection.STATE_DIALING);
         }
 
+        @Override
+        public void setPulling(String callId) {
+            findConnectionForAction(callId, "setPulling")
+                    .setState(Connection.STATE_PULLING_CALL);
+        }
+
         @Override
         public void setDisconnected(String callId, DisconnectCause disconnectCause) {
             if (mConnectionById.containsKey(callId)) {