Make specs less timeout dependent

Got the specs running reliably now, but had to re add Adapter#shutdown.
Because of eventmachine the before and after blocks in adapter_lint.rb are a mess now,
would really appreciate it if someone can come up with a cleaner solution.
I think you won't need to do any cleanup, Thread#kill should destroy everything cleanly. It might be worth trying out Thread#raise though, in case the EventMachine reactor is behaving funnily. Errors should bubble up and properly trigger EM's self-destruction.