nettests: remove most of connectivity checks

With its default connectivityCheck=True, setupNetworks wait for a ping
before finishing successfully. This slows down the functional tests.
It is important to keep testing connectivityCheck, but it does not have
to happen so often.

Change-Id: I1895d266dfb2d7f8ca7dcff860e0d96b1fc07e14
Signed-off-by: Dan Kenigsberg <danken@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/24167
Reviewed-by: Antoni Segura Puimedon <asegurap@redhat.com>