Ansible launcher: use underscores where appropriate
Ansible launcher: use underscores where appropriate

Zuul config file options and zuul gearman functions both use
underscores.  Switch to those before this gets out of hand.

Also use getboolean for getting the boolean config option.

Change-Id: Ibecf6b9f0786860e4a0d8653ce5c210dd11a9971

wikimedia/integration-zuul,gooddata/zuul,gooddata/zuul,gooddata/zuul,gooddata/zuul,wikimedia/integration-zuul,wikimedia/integration-zuul,wikimedia/integration-zuul,gooddata/zuul