Use tempest tox with regex first

This commit add regex first while running tempest tox

There is changes in way tempest tox runs tests by using the tempest run
command directly instead of some bash script.

With tempest run you specify a regex with a '--regex' parameter and to
keep backwards compatibility this is added to the tempest tox
definitions.

But in Nova tests scripts it is being used after concurrency and ends up
having a call equivalent to:

  tempest run --regex --concurrency=2 $tempest_regex

which obviously is incorrect. Simply switching the arg order should work here.

Change-Id: If0064b9e8358332972ef4a1eee8f150e66f8c50f
Needed-by: I3684fce66a799579fa68af119652cafef25a9f03

nova/tests/live_migration/hooks/utils.sh

@@ -3,7 +3,7 @@
 function run_tempest {
     local message=$1
     local tempest_regex=$2
-    sudo -H -u tempest tox -eall -- --concurrency=$TEMPEST_CONCURRENCY $tempest_regex
+    sudo -H -u tempest tox -eall -- $tempest_regex --concurrency=$TEMPEST_CONCURRENCY
     exitcode=$?
     if [[ $exitcode -ne 0 ]]; then
       die $LINENO "$message failure"