libbinder: RPC avoid FdTrigger shutdown race

RpcSession's FdTrigger can't have simultaneous calls to trigger. This
will cause a double-close of the FD. Take locks to avoid this case.

Bug: 200368820
Test: binderRpcTest, binder_rpc_fuzzer, binder_bpBinderFuzz
Change-Id: I94822f441142b3a1352e38adacb8e17f285d66ac
1 file changed