CCodec: ignore input buffer done callbacks before flush

These callbacks will clear buffer references that stashed
codec config is holding onto.

Bug: 196014695
Bug: 199818561
Test: cts/media/device-small
Change-Id: I9c04aaff26ad5e4f8b66e341e2098e863c1ce314
diff --git a/media/codec2/sfplugin/CCodecBufferChannel.h b/media/codec2/sfplugin/CCodecBufferChannel.h
index d2862bd..26eef30 100644
--- a/media/codec2/sfplugin/CCodecBufferChannel.h
+++ b/media/codec2/sfplugin/CCodecBufferChannel.h
@@ -273,6 +273,7 @@
         size_t numExtraSlots;
         uint32_t inputDelay;
         uint32_t pipelineDelay;
+        c2_cntr64_t lastFlushIndex;
 
         FrameReassembler frameReassembler;
     };