(SERVER-151) Move environment fns from jruby-testutils to service

We originally defined some functions for interacting with the
environment cache state in jruby-testutils.  This commit moves
the logic into the `JRubyPuppetService` instead; this will be necessary
in order to wire up the HTTP endpoint, since we will only have
access to the service and not to the entire TK app.
Merge pull request #277 from cprice404/feature/master/SERVER-151-flush-env-cache-from-service

(SERVER-151) Move environment fns from jruby-testutils to service