For some reason, an env variable's (RUN_TESTS_EXTRA_ARGS) default value
was not properly overwritten on these testenvs.
Its default value has been removed, since it's not relevant for other
testenvs.
Besides this, the marker skip_during_ovn_migration has been added to the
test test_equal_containers_state because it should not be executed after
ovn-migration (list of containers changes, so comparison between
previous and new containers is not relevant).
Also, the background ping test will be skipped for ovn_migration and
ovn_migration_sanity testenvs because the may be traffic loss during the
migration process.
Change-Id: I71de87e5216ac2d6c7e198ea6236fe189b79408d
2945010168