wan: fill in wan ipv4 addr to wan6 when establishing 6in4 tunnel
requested to merge 197-6in4-connectivity-cannot-specify-the-public-ip-address-in-case-the-user-is-behind-1-1-nat into master
Closes #197 (closed)
Should fill current wan ipv4 address to wan6 interface (missing 6in4 endpoint ipaddr <-> peeraddr).
Afterwards 6in4 should start working (at least that was my case).