config: recheck have_link_local on interface reload if already init

config: recheck have_link_local on interface reload if already init

If an interface is already init in the odhcpd avl tables, have_link_local
is not set to true with a link local addr set as get ipv6 addr is skipped.

Move checking for have_link_local outside get_addr to better track when
an interface is ready and have a link local addr for interface already
init in odhcpd avl tables.

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