Convert all MPU related operations to HA model

In this jira, we shall convert all OM related operations to OM HA model, which is a 2 step.

1. StartTransaction, where we validate request and check for any errors and return the response.
2. ApplyTransaction, where original OM request will have a response which needs to be applied to OM DB. This step is just to apply response to Om DB.

In this way, all requests which are failed with like volume not found or some conditions which i have not satisfied like when deleting volume should be empty, these all will be executed during startTransaction, and if it fails these requests will not be written to raft log also.