Test harness should support watching objects rather than polling

[jbarrick-mesosphere]

Currently, the test harness polls for object state when tests are running which offers opportunity for races (and is likely more inefficient). For example, to test delete steps in KUDO properly, we need to be able verify that a Job is created and is completed before it gets deleted, without racing KUDO, if we poll, there is a chance we can miss the Job before KUDO deletes it.

[kensipe]

Need to put some thought into this... Sounds like we should target this soonish