dhcp6: start when link-up + link-address ready

Fixed to not wait until network is up. Wait until the
link is up, then for a non-tentative link-address and
trigger the transmissions.
Reset the fsm on network/link-down, not the config.
wireless: do not remove link/network up flags

Do not remove link/network up flags from device flags
when not in established state, which are IMO correctly
maintained by the kernel/wpa_supplicant already.
radv: show RA hint event info in debug2 level only
dhcp4: omit arp validation if address is on link
dhcp4: modprobe af_packet module at start

In hope this makes the gap after link-up shorter.
dhcp4: check if link is up before start

Also try a quick renew of existing lease at start
dhcp4: do not discard lease if host does not match

The dhcp server may return the requested hostname
or completely another one or no hostname at all.
dhcp4: confirm lease after link change or restart

Dropped fail_on_timeout flag and renamed fsm_quick_renewal to
fsm_reboot to confirm lease using broadcast as defined in the
RFC2131 (3.2, reusing a previously allocated network address).
dhcp4: removed unused renew-requested state flag
Merge pull request #160 from mtomaschewski/wlan-states