tests: adding missing cleanup decoration

Some tests need to cleanup the env in case of failure.
This patch adds the missed cleanupNet decoration to
some tests.

Change-Id: I0774f901f654022080d39c486a1dd6d6d7f021fb
Signed-off-by: Giuseppe Vallarelli <gvallare@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/18606
Reviewed-by: Antoni Segura Puimedon <asegurap@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>