[rfr]Fix api interfaces for orchestration resources

[pratikmallya]

Some of the interfaces don't correspond well to the values
expected by the requests and returned by api.

depends on: #478
corresponds to: rackspace/rack#324

[jrperritt]

@pratikmallya Because of the built-in way Go handles package management (via go get), it's important that we are aware of backwards-incompatible changes that aren't bugs. For example, the issue of having the wrong time format I'd consider a bug, because users could not have gotten that working with their own code. Also, adding fields and functions/methods is also fine. However, changing types and removing fields is a bit more sensitive. For each of the changes in this PR where you changed a data type or removed fields, can you provide an explanation for why? When the orchestration service was implemented, it was coded against the docs here and here and tested against devstack and Rackspace public endpoints. I know the documentation may not reflect reality, but, if not, we need to know that.

[pratikmallya]

@jrperritt good point. I will add comments to clarify why I made the changes.

[pratikmallya]

This change should have been in #466. Apologies

[pratikmallya]

@jrperritt I added comments to the code where I changed the interface significantly. Let me know if you need more context.

[pratikmallya]

@jrperritt can you please take a look?

[pratikmallya]

Closing, since commit is included in #486