Essentially, if DHCPv6 only is desired, then anaconda should make sure to explicitly disable IPv6 autoconf, otherwise the autoconf default depends on what the forwarding values are. Better to be explicit and add IPV6_AUTOCONF=no in this case instead.
This should be fixed in anaconda-13.21.75-1.
With snap #12 the ifcfg-eth0 file has:
Moving to VERIFIED.
Red Hat Enterprise Linux 6.0 is now available and should resolve
the problem described in this bug report. This report is therefore being closed
with a resolution of CURRENTRELEASE. You may reopen this bug report if the
solution does not work for you.