DO NOT MERGE SF: Fix releaseBufferEndpoint merge issue

If a transaction contained a cached buffer, and was
parcelled then merged, the releaseBufferEndpoint would
not be merged correctly. This would result in SF not
releasing a buffer and the app eventually ANRing.

DO NOT MERGE because this issue doesn't exist in master

Bug: b/205791752
Test: manually rotate apps to trigger sync
transactions and check the logs to see
we don't release stale buffers. Real tests to
follow

Change-Id: Ibd295be5e06fea00b331610206f1664f651afed3