Add unit tests for nginx runtime manager

[sjberman]

trafficstars

As a developer, I want my code to be thoroughly unit tested, so that I can ensure that everything works as expected.

The nginx runtime manager is lacking in unit test coverage.

Acceptance

• Add unit tests to thoroughly cover the nginx runtime manager code

Dev notes

• will likely need mocks for nginx plus client and "verifyClient"
• use ginkgo since we're testing interfaces