Coordination of logical device and task assignment for voltha core

To support high availability it is essential that, in the event of a failure, any lost component's tasks can be taken over by another.

Each voltha core is responsible for managing multiple logical switches. In the event of a failure, the tasks being performed by the failed core need to be taken over by another core. The coordinator ensures that these tasks are taken over by one and only one alternate core. This becomes critically important if a cluster member fails and multiple cores are lost.

Acceptance Criteria:

• Bring any number of voltha instances up (with persistence enabled)
• Perform any number of operations on each voltha instances
• Bring any number of voltha instances down
• Create new voltha instances
• Verify that the new instances have picked up the workload of the instances that were brought down.