New network config for integration tests

[Marius Vollmer]

Hi,

we are still fighting with the regressions caused by my careless test
image updates.

We had to change the configuration of the virtual "cockpit" network used
by the tests to avoid some weirdness re DCHP.

You need to destroy it and create it again.  As root:

# cd .../cockpit/test/
  # ./vm-prep -u
  # ./vm-prep