Disable IPv6 automatic SLAAC by linux kernel and handle it manually.
This allows us gaining control on local address acquisition and set
addresses and routing properly. It will also allow us to run in ping
mode without a tun iface.
Related: OS#4434
Change-Id: Iae59cf6ffb181357e10b3080a5c751bd454f4a1f
Functions for IPv6 will be added soon afterwards. Also take the chance
to check for address length in sgsnemu and only apply the route if the
address matches.
Change-Id: Ic6c1b3c11c56f047e6e8c6f1040257fd62afea0f