The network tests were expecting that network interfaces
are in certain order. As we cannot guarantee that, refactor
the tests like this:
* if test is using DUMMY L2 driver, then disable Ethernet L2
and fetch only DUMMY L2 instead of default interface
* if test is using Ethernet L2 driver, then make sure that the
test is using the Ethernet interface specified in the test
instead of the one provided by the DUT
Fixes#34505
Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>