Fix bugs in ipv6 PBR

Two bug fixes regarding IPv6 PBR (commit : https://github.com/vyos/vyatta-quagga/commit/8fad8bae1fecf0725f5e931d5f3337ccb9d5ec88)

First, in vtysh, "show running-configuration" would not print ipv6 routes in non default tables.

Secondly, ipv6 routes in a non default tables were not being updated when interfaces changed status. For instance, when using ppp interface, zebra would mark the routes as "inactive" while the interface appears down. When the interface comes up, zebra calls rib_update() to mark routes as active. Before this patch, only the main ipv6 routing table was updated by rib_update(). Every table is now.

This should close #168.