route: test that routes with custom table are cleaned up
NM was only cleaning routes in main table when doing reapply or connection down. Fixed in 1.51.5, so add tests to avoid regressions.
NetworkManager!2080
Related: https://issues.redhat.com/browse/RHEL-67324
Related: https://issues.redhat.com/browse/RHEL-66262
Resolves: https://issues.redhat.com/browse/RHEL-69488
Edited by Íñigo Huguet