config: use dedicated link local function to check interface

config: use dedicated link local function to check interface

Use netlink_get_interface_addrs is wrong and doesn't actually work. The
function checks only for UNIVERSE address and is not suitable for
dumping linklocal address of an interface. Use the new and dedicated
function to get interface linklocal address to correctly check if the
interface can receive message.

Fixes: #197
Fixes: 7c0f603abc14 ("router: skip RA and wait for LINK-LOCAL to be assigned")
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>