Really disable IPv6 RA processing in dhcpcd.

IPv6 RA processing in dhcpcd causes crashes, so we disabled it in
dhcpcd.conf. Unfortunately devices sometimes don't have the
config file, because one is not required for dhcpcd to work. So
disable IPv6 RA processing in the code too.

Bug: 15268738
Bug: 15779617
Change-Id: If3f904dc8a9cda9bdbf2ce424c4a3ecbb4c88fee
1 file changed