CLOUDSTACK-2517: fixed private gateway creation. Following fixes went in:

1) Only PrivateNetworkGuru handles network creation for the private gateway. Exluded Guest Network Guru from this list (was mistakenly included as a part of merge for Nicira integration)
2) Pass vpc_id to createNetwork call when the network is created as a part of private gateway creation
3) Fixed VPC restart when there are multiple private gateways present (have to grab all the private gateways when creating nic profiles for the VPC router that is being re-created)
4) 41-42 db upgarde: set vpc_id for the private networks of the existing VPCs
CLOUDSTACK-2519: VMs on local storage incorrectly destroyed when removing another host using deleteHost API

- For DeleteHost API: Search for Volumes in READY state on the local storage of the host to find VM's in 'Running' State
- For PrepareForMaintenance API: Search for Volumes not in Destroy or Expunging state to check if the Local Storage on the host is being used.