[FT] Move BaseOVSTestCase class to concurrency 1 executor

Move the ``BaseOVSTestCase`` class tests to the stestr executor with
concurrency=1. That will prevent that the minimum bandwidth tests
interfere among them.

Conflicts:
    tox.ini

Closes-Bug: #2025740
Change-Id: Ia3741abe5fa0c8ff65cf36d1ec31c089a1759f05
(cherry picked from commit 26a2266)

Author: ralonsoh

tox.ini

@@ -79,8 +79,8 @@ setenv = {[testenv:dsvm-functional]setenv}
 deps = {[testenv:dsvm-functional]deps}
 commands =
   bash {toxinidir}/tools/deploy_rootwrap.sh {toxinidir} {envdir}/etc {envdir}/bin
-  stestr run --exclude-regex (.*MySQL\.|.*PostgreSQL\.|.*test_get_all_devices) {posargs}
-  stestr run --combine --concurrency 1 (.*MySQL\.|.*PostgreSQL\.|.*test_get_all_devices) {posargs}
+  stestr run --exclude-regex (.*MySQL\.|.*PostgreSQL\.|.*test_get_all_devices|.*BaseOVSTestCase\.) {posargs}
+  stestr run --combine --concurrency 1 (.*MySQL\.|.*PostgreSQL\.|.*test_get_all_devices|.*BaseOVSTestCase\.) {posargs}
 
 [testenv:dsvm-fullstack]
 setenv = {[testenv]setenv}