Some tests are skipped because the public network is not shared.
Enabling 'shared' option for the network will allow the tests to run.
Enabled dhcp on the public subnet to allow VMs connected to it
obtain ip addresses successfully.
Both changes above are applied only for ovn jobs since for ovs jobs
additionally require some additionall settings, e.g. to ensure that
only a single dhcp server exist on external network. This can be done
in a separate patch if needed.
Adjusted bw_limit external network qos test to use a separate VM on
external network instead of sending traffic from the test container
in order to not depend on specifics on different environments.
Change-Id: I2e6cf51a4dab7eb593362d482e2587d54e4a12d6
cc3958263c