1) Added comments to VPC/VPCService/VPCManager interfaces
2) Moved VPC offering related methods from VpcService to the new interface - VpcProvisioningService
3) Fixed static nat creation in the VPC - used to result in NPE due to invalid method referencing while obtaining VPC VR information
The new policy is:
1. Generate a random IP.
2. Find the next available IP, start from the generated IP.
3. If we cannot find an available IP after certain times(10000 by default,
network.ipv6.search.retry.max) retry, give up.
Also ass public_ipv6_address for ipv6 address management.
Extend nics and vlans for ipv6 address.
Add dependency to com.googlecode.ipv6(java-ipv6).
Modify dhcpcommand for ipv6.
NetworkServiceImpl does not need a cache of system network offerings
Ensure mocks build to new APIs.
Signed-off-by: Chiradeep Vittal <chiradeep@apache.org>