Call hangup(CallManager) while handling headset hook.

For bug 3028772.

While handling the long press action of headset,

it should call hangup(CallManager) instead of hangup(ringingCall) to

hangup foreground call or background call.

Change-Id: Ia7ea715842c544aee72af08084e39377a33b36ad
diff --git a/src/com/android/phone/PhoneUtils.java b/src/com/android/phone/PhoneUtils.java
index 498fb15..ebfaf49 100644
--- a/src/com/android/phone/PhoneUtils.java
+++ b/src/com/android/phone/PhoneUtils.java
@@ -1919,7 +1919,7 @@
             // No incoming ringing call.
             if (event.isLongPress()) {
                 if (DBG) log("handleHeadsetHook: longpress -> hangup");
-                hangup(phone.getRingingCall());
+                hangup(PhoneApp.getInstance().mCM);
             }
             else if (event.getAction() == KeyEvent.ACTION_UP &&
                      event.getRepeatCount() == 0) {