Have sync-tests send PID directly to runner.

The sync tests already have a socket to the testrunner. It should use
it to directly send the tests pid to the runner for stack-trace
dumping if the test fails.

Test: ./art/tools/run-libjdwp-tests.sh --mode=host
Bug: 70838465
Change-Id: Id1cc23be83c3de52e7341f3b430866be8772795c
3 files changed