OSD orchestration should return success to the leader immediately after it starts config

[travisn]

Device initialization for OSDs takes on the order of minutes. For the agent to configure all devices before returning to the orchestration leader causes several problems:

• Orchestrations are blocked for a long period of time
• New machines coming online may have to wait a long time to be configured
• More critical services such as etcd and ceph mons will be blocked from failover orchestration for long periods of time.

Completion of OSD configuration is a process that is quite independent from core orchestration. The only thing the orchestrator really cares about is whether the agent is actively configuring the OSDs. There are no orchestration failover scenarios that OSDs need to worry about, unlike the more critical etcd and mon services.

Upon a request to configure OSDs, the agent can immediately return success to the orchestrator that it is working on the configuration. There is no need to wait for all the OSDs to complete.

For applications that need to be guaranteed there is storage available (ie. OSD configuration is complete), the orchestrator can provide a helper to signal progress of available OSDs.

[travisn]

Fixed by #140