Fix ipv6 route table base calculation
Fix ipv6 route table base calculation

Wrong pointer math made ipv6 route table base to overlap with ipv4 route
table, resulting in unpredictable tables and memory corruption.

Change-Id: Ia31a555cf3abb108af31c1ee74c4cd7384570de6
Closes-BUG: #1439654

codilime/contrail-vrouter,codilime/contrail-vrouter,codilime/contrail-vrouter,codilime/contrail-vrouter