[Weighted Round Robin] Support for API versioning

[Bukhtawar]

Is your feature request related to a problem? Please describe.
There is a possibility that during zonal code deployments these weights have to be modified. Its possible multiple use cases around new zone provisioning/removal/updates can result in concurrency issues. Then its also possible that we fail over traffic from one zone to another in the face of a zonal outage while a provisioning/deployment is underway which might lead to nasty failures

Describe the solution you'd like
We can support versioning in the API and support weight updates iff the versions read is the same that is being modified.
Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.

[shwetathareja]

@Bukhtawar thats a good point. I think we should think about Optimistic Concurrency Control across all administrative APIs in general which are operated by ClusterManager as order of request queuing from client would be different from how it lands up in master pending tasks queue and eventually executed.