[OC-10514] Update keepalived to be IPv6 friendly.

Keepalived 1.1.20 won't manage a IPv6 VIP. Upgrading to 1.2.9 pulls in
a large amount of IPv6 work (1.2.0 1.2.8 and 1.2.9 all contain fixes)

Upgrading to 1.2.9 also appears to obsolete our patches to ntohl; line
968 of vrrp.c looks like our patch.

From the changelog (http://www.keepalived.org/changelog.html), it
looks like there have been updates to the unicast code in 1.2.8 and
1.2.9, which may also obsolete our unicast patch. However this
probably will require testing, and perhaps changes to our
configuration process.
Patch to build on centos 5.5. Obsolete when we upgrade beyond 1.2.9

Older versions of the kernel lack the IFA_F_NODAD flag, which causes build failures. This flag improves failover behavior, but is not required for correct performance.

This was taken from a patch merged to master, and will be unnecessary soon.