Fix object pool for lifecycler

The original implementation of object pool for lifecycle
transactions tried to always recycle objects after a
transaction was scheduled. In case when a client was running
in the same process this lead to objects being emptied before
it could actually perform the transaction.
Also when checking if object was already in the pool we should
use "==" instead of equality check.

Bug: 70554032
Bug: 71346774
Test: com.android.server.am.ClientLifecycleManagerTests
Test: android.app.servertransaction.ObjectPoolTests
Change-Id: I85fb3dae4589c2390e00a37144da0d285d16d151