libbinder fuzzService: can't start threadpool

Should also check libhwbinder comms, rpc binder comms,
and other types of communication, but it may be difficult,
may require additional dependencies to these fuzzers. For
now, prevent the obviously problematic things we can
detect immedately.

Bug: 242905949
Test: android.hardware.vibrator-service.example_fuzzer

Change-Id: Icdc7ba4f1df6efe05a60ecc7afb697180ba1a1bb