Deal with additional conditions properly

[marcoderama]

These changes are a fix for Issue #536.

The fundamental diffs are

• Make the Status component optional in both StatefulStores and StatefulServices. This is the natural condition when they're first created.
• Fix up ReconcileStatefulServiceConditions()

After these changes, and testing with the setup of Issue #536, the StatefulService entity ends up with a Status section looking like:

status:
  conditions:
  - lastTransitionTime: "2021-02-18T01:15:21Z"
    message: Stateful store no-store not supported
    reason: StoreNotSupported
    status: "True"
    type: NotReady
  - lastTransitionTime: "2021-02-18T01:25:22Z"
    message: Application is in the process of updating
    reason: UpdateInProgress
    status: "True"
    type: NotReady

[marcoderama]

Tests now pass but converting to draft because I want to reconsider making the Status component optional.