ovs: Change default bridge names

ovs: Change default bridge names

Default names of OVS bridges used by vsperf were changed
to avoid accidental collision with 3rd party bridges
(e.g. linux bridges) already configured at DUT.
Step driven testcases, which extend existing deployment
scenarios, were updated to use appropriate configuration
options instead of hardcoded bridge names.

JIRA: VSPERF-580

Change-Id: I8c7eee6d8f6532485ec3a2cc06f26515e665fb7e
Signed-off-by: Martin Klozik <martin.klozik@tieto.com>
Reviewed-by: Al Morton <acmorton@att.com>
Reviewed-by: Christian Trautman <ctrautma@redhat.com>
Reviewed-by: Sridhar Rao <sridhar.rao@spirent.com>
Reviewed-by: Richard Elias <richard.elias@tieto.com>