Add failing test for ObjectWrap->Ref() race condition

Causing memory pressure _sometimes_ hits a race condition where the GC kicks in before the connection is finished reading. This causes a segfault or other unprotected memory errors.

Also refactor tests to make sure they cleanly exit. Cleanly exiting is crucial to test proper GC behavior with new node-libpq bindings which change the #Ref() & #Unref() behavior.
Add test for many errors