Revert "libbinder: Flush excess refs after single async transaction"

This reverts commit 6aae5369.

Reason for revert: b/268238590
Bug: 268238590
Test: binderRpcTestNoKernel --gtest_filter="*OnewayCallQueueingWithFds/unix_domain_socket_bootstrap_raw_clientV4026531840_serverV4026531840_no_kernel*" --gtest_repeat=10000 --gtest_break_on_failure

(this change causes tests to flake, reverting for now)

Change-Id: I2dd4e347228791085f3f2534f948839ee27c16b6