Sync bug fixes from Grizzly into Havana.

Fixes the following bugs:
1. Remove unncessary RPC calls.
2. Send delete subnet request to VSM on VSM failures for ip pool.
3. Add dns nameserver list and dhcp information in subnet create
   and update.
4. Update subnet properties to VSM.
5. Fix network delete. Solve merge conflict.
6. Throttle requests to VSM.
7. Get rid of network_vlan_ranges to sync vlan and vxlan allocations.
8. Fix VSM-Neutron database sync issues.
9. Remove list events and instead use list profiles api from VSM.