Fix broken long-running sims

The code for the long-running sims was broken.  There was a mutable
class variable that was being manipulated by multiple different
gatling "users" on the same instance of the class.

Also, Thread.sleep is a huge no-no in async code.  Now we're using
the gatling "pause".
Merge pull request #22 from cprice-puppet/bug/master/PE-634_broken_sleep

Fix broken long-running sims