Allow DHCPv6 solicit from VM

DHCPv6 solicit UDP package is currently dropped because
there is no security group rule to allow it like IPv4.

This fix allows UDP DHCPv6 solicit from client port 546 to
server port 547. This fix also drops DHCP reply from VM.

Change-Id: I4941d401576e2c8bad37859d2cba227afde9e764
Closes-Bug: 1316515
Merge "Allow DHCPv6 solicit from VM"