Fix unexpected FrameEvents on BufferQueue reconnect

Helps reduce the number of ALOGE's being hit
when switching between apps.

* Notify Layer when the Producer disconnects.
* Avoid sending event deltas from a previous connection.
* Avoid releasing a frame more than once.

Test: adb shell /data/nativetest/libgui_test/libgui_test
    --gtest_filter=*GetFrameTimestamps*

Change-Id: I64f314be72ddb154b584d726ac382cd468e345bf
diff --git a/libs/gui/BufferQueueProducer.cpp b/libs/gui/BufferQueueProducer.cpp
index 3f69b1f..be0dc20 100644
--- a/libs/gui/BufferQueueProducer.cpp
+++ b/libs/gui/BufferQueueProducer.cpp
@@ -1272,6 +1272,7 @@
     // Call back without lock held
     if (listener != NULL) {
         listener->onBuffersReleased();
+        listener->onDisconnect();
     }
 
     return status;