Fix build-up of duplicate IPv6 routes on reconnect.

Fix build-up of duplicate IPv6 routes on reconnect.

options.c: extend pre_pull_save() and pre_pull_restore() to
	   save/restore options->routes_ipv6 as well
options.h: add routes_ipv6 to "struct options_pre_pull"
route.h, route.c: add clone_route_ipv6_option_list() and
	   copy_route_ipv6_option_list() helper functions

Signed-off-by: Gert Doering <gert@greenie.muc.de>
Acked-by: David Sommerseth <davids@redhat.com>
Signed-off-by: David Sommerseth <davids@redhat.com>