separation of engine ops and validation of params

[pferrel]

we should add better synchronous validation when engine ops happen now that they are async.

[pferrel]

With etcd we have moved the validation of engine params into the deferred processing of the engine-add notification. In the past validation was synchronous with the engine-add command and there was no notification. The effect of this separation of validation means virtually no validation happens synchronous with the angine-add REST call. We can refactor this is to support more validation.

engine add, and update are affected

[pferrel]

only applies to Harness 1.0+