net_func_tests: add test for reconfiguring broken bridged network

This test checks that bridged networks with missing ports are
successfully redefined on command. It is related to the syncing
issues described in https://bugzilla.redhat.com/861701

Change-Id: I1e1895d0b6724870f38529a3c04224103d60828d
Signed-off-by: Antoni S. Puimedon <asegurap@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/28529
Reviewed-by: Dan Kenigsberg <danken@redhat.com>