fix(test): improve test 60

fix(test): improve test 60

The test has the following issues:

 - it sets up a bridge on net1 and net2, however those interfaces
   are part of the same qemu hub and this causes switching loops;

 - the bonds are created on two interfaces but only one has a DHCP server, and
   this causes random failures;

 - the checks performed on the client are pretty limited.

Rework the test:

 - avoid the bridging loop;

 - update the topology to use a bond interface on the server side;

 - introduce additional checks on the client: start a ping and check that ports
   are properly attached to bonds and bridge;

 - make it possible to return module-specific information from the client; in
   the future this can be added for example to check that the NetworkManager or
   systemd-networkd configuration is correct.