Add share-network activation api

Current design assumes creation of VM (Vserver) with "share-network" data on first share creation, and we can not delete it after. (see https://bugs.launchpad.net/manila/+bug/1273758)

So, we should have possibility to explicitly create VM (Vserver), consider 'activate' share-network and delete Vm (Vserver), consider 'deactivate' share-network.

So, share network should have next api:
- create
- deletу
- activate (new)
- deactivate (new)
- assign security service
- remove security service
- update share-network
- list assigned security services
- show share network
- list share networks

Requirements for new api:
1) For activation of share-network, it should be in INACTIVE state.
2) For deactivation of share-network, it should be in ACTIVE state and has no dependent shares. After deactivation, VM (Vserver) will be deleted and manila will release allocated resources, that has been allocated for its purposes.
3) Share network can be deleted with any state except "ACTIVE".
4) if activation fails, share-network gets "error" state.
5) share-network in "ACTIVE" state can be updated, but only "name" and "description fields"
6) Any field of share-network can be updated, if that share-network is in any state except "ACTIVE".