don't check workers at init

we want to be able to allocate a MyriaConnection even if the server
isn't up.
for now, put default query count back in

so I can move forward with myria-web before uwescience/myria#436 is
merged.
tests: remove unnecessary /workers

We don't check /workers at connection creation any more.
test: stop using real ports

So we don't get bad results if improperly mocked and local deploy
running
Assert that the x-count header exists when getting queries