this removes the following warning:
```
DEPRECATION: `config.poll_interval = 0.5` will be removed in Sidekiq 4. Please update to `config.average_scheduled_poll_interval = 0.5`.
```
Requiring sidekiq/testing changes stuff, so we need to counteract that
after we do so.
And given its potential to confuse things, let's do it up front, at a
predictable point.
Sidekiq::CLI#boot_system require "#{dummy_app_path}/config/environment.rb".
But this file has already been required in'test/support/integration/helper.rb'.
This patch will change to use Sidekiq::Launcher directly.
* .connect on a Redis connection wasn't valid
* Reset logger after we're done testing for redis connection to avoid
"closed stream" error when starting server for real from a fork
