- hardcore force every connection into a strong-referenced set, rollback on every...

- hardcore force every connection into a strong-referenced set, rollback on every test, close on every context.
this uses pool events but bypasses the pool's fairy/record/dispose services.   pypy still seems to expose
some holes in that at least as far as what some (or maybe just one, cant find it yet) of the tests does.
haven't tested this too deeply, just on sqlite + postgres, cypthon 2.7 + pypy.   will see what the buildbot
says