Remove --isolated flag from functional tests

The --isolated flag in stestr run was sequentially running test,
after some round testing without that parameter, test are passing
running in parallel. Make sense to remove to reduce drasticallly the
time of the job.

Change-Id: I914218b487be8bd90d9d62337e04060b6c6eed05
Signed-off-by: Fernando Royo <[email protected]>

Author: fernandoroyosanchez

tox.ini

@@ -64,7 +64,7 @@ passenv =
   {[testenv]passenv}
   OS_TEST_DBAPI_ADMIN_CONNECTION
 commands =
-  stestr run --isolated {posargs}
+  stestr run {posargs}
 
 [testenv:cover]
 setenv =