This change adds relations necessary for registering a compute cell
with the superconductor. For a cell to be registered this charm
must have relations with the compute cells conductor, database and
message queue. Only when all these relations are complete can the
registration happen. Below are major changes included in this PR.
* Add nova-cell-api relation for communicating with the
nova-cell-conductor
* Add shared-db-cell relation for communicating with the
a compute cells database.
* Add amqp-cell relation for communicating with the
a compute cells message queue.
* Add methods for registering cells with the
superconductors database.
* Charm helper sync
Change-Id: Ic6ddc29426319b98b147c29031f60485fccc513f
