API: Adding the ownership implmentation to storage_service
API: Adding the ownership implmentation to storage_service

This adds the ownwership method implementation to the storage_service
API. After the patch the following url will be supported:

GET /storage_service/ownership/{keyspace}
GET /storage_service/ownership/

Signed-off-by: Amnon Heiman <ed5fc74c4692051ad0b19749fd7cea6ec2d74b9e@cloudius-systems.com>

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