Bug #1244589 re-appeared for IPv6.
This change adds an ip6tables rule to fix the checksum of DHCPv6
response packets. Those checksums were left unfilled by virtio (as a
hypervisor internal optimization), but some picky dhcp clients (AFAIU
particularly ISC dhclient) try verifying the checksums, so they fail
to acquire an address if the checksums are left incorrect.
Change-Id: I4a045e0dcfcbd3c7959a78f1460d5bf7da0252ff
Closes-Bug: #1811639
Related-Bug: #1244589
(cherry picked from commit 26eb2509fe)