Added object caching and multi-threading to CLI tests
I chose to have the caching off by default.
Initial tests show time savings between 4-8 minutes for all CLI
tests.
Caching is made available through the @cacheable decorator.

Also threw in multi-threading capability. No additional errors produced.
Time results will vary per machine, but my test time was reduced from
approximately 5 hours to around 40 minutes.

Use make test-foreman-cli-threaded.
Ran 1114 tests in 2416.224s