Backport monitored_environments support from upstream

This will allow us to specify which environments we want nagios to monitoring
(i.e. the openstack envs and production).
Update download URL for plugins
Test kitchen support for server testing
Add some basic tests

NOTE: The hostgroups should include all environments as intended. The upstream
patch did the same thing.
Switch to using regex for pattern matching
Merge pull request #3 from osuosl-cookbooks/ramereth/monitored-envs

Backport monitored_environments support from upstream