dhcpv6: fix solicit loop when server has no address available

dhcpv6: fix solicit loop when server has no address available

Problem: If Advertise with status 'noaddravail' is received while IA_NA
is requested, a new Solicit is sent creating an infinite loop.

Solution: Set IA_NA mode to none and send INFO-REQ message if no IA_NA
or IA_PD are available.

Signed-off-by: Nicolas BESNARD <nico.besnard31@gmail.com>
Signed-off-by: Paul Donald <newtwen+github@gmail.com>
Link: https://github.com/openwrt/odhcp6c/pull/106
Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>