iproute2: ip addr: Add support for setting 'optimistic'

optimistic DAD is controllable via sysctl for an interface
or all interfaces on the system. This would affect addresses
added by the kernel only.

Recent kernels, however, have enabled support for adding optimistic
address via userspace. This plumbs that support.

Signed-off-by: David Ahern <dsahern@gmail.com>
2 files changed