Fixed validation of create_and_list_trunk_subports rally scenario

New validation now enforces that times is >= concurrency because times
is total number of *runs*, not the number of concurrent *run sets*.

Change-Id: I454ef821e00bd5123a9640f472ad4b034dbec75e
Closes-Bug: #1680580

rally-jobs/neutron-neutron.yaml

@@ -311,7 +311,7 @@
         subport_count: 250
       runner:
         type: "constant"
-        times: 1
+        times: 4
         concurrency: 4
       context:
         users: