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
diff --git a/telecomm/java/android/telecom/RemoteConnectionService.java b/telecomm/java/android/telecom/RemoteConnectionService.java
index 21a7706..306b3c1 100644
--- a/telecomm/java/android/telecom/RemoteConnectionService.java
+++ b/telecomm/java/android/telecom/RemoteConnectionService.java
@@ -118,6 +118,12 @@
         }
 
         @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)) {
                 findConnectionForAction(callId, "setDisconnected")