test/socket_netlink_route: check that there is a route on local or main tables
test/socket_netlink_route: check that there is a route on local or main tables

A new network namespace has only the local route table.

PiperOrigin-RevId: 324303629

google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor