libbinder_ndk: fix UB memory access for race

AIBinder_DeathRecipient holds a strong pointer to its internal class
TransferDeathRecipient. If a user deletes a death recipient at the
same time a binder dies, the TDR still holds a reference to the
AIBinder_DeathRecipient object that may be invalidated.

Bug: N/A
Test: build, boot, and ./runtests.sh
Change-Id: Ic4cbc50c2d85ce52e36d4b157a50d0c75048e664