On clusters configured with dual-stack network the
IPv4 and IPv6 addresses can be added to the main interface
at different time, which results in the openshift node addresses
not containing the IPv6 address. This commit fixes the issue
by including `ip=dhcp,dhcp6` to the kernel args of masters and works,
which sets `required-timeout` to an value that the IP configuration
will be tried before succeeds. This configuration is valid for day1
dual-stack clusters only.
