Fix pre_test_hook in rally-scenarios-job

pre_test_hook.sh should be run in the current shell context. This is
mandatory because we need to export some environment variables.

Also fixed `voting` line for this job.

Change-Id: I49632bd323ad7abdcfaff5d8295a4557fa8e34ec

modules/openstack_project/files/jenkins_job_builder/config/rally.yaml

@@ -22,7 +22,7 @@
           export PROJECTS="stackforge/rally $PROJECTS"
 
           function pre_test_hook {{
-              /opt/stack/new/rally/tests_ci/pre_test_hook.sh
+              . /opt/stack/new/rally/tests_ci/pre_test_hook.sh
           }}
           export -f pre_test_hook
 

modules/openstack_project/files/zuul/layout.yaml

@@ -549,7 +549,7 @@ jobs:
     voting: false
   - name: ^check-rally-install-.*$
     voting: false
-  - name: ^check-rally-scenarios-.*$
+  - name: check-rally-scenarios
     voting: false
   - name: gate-rally-python33
     voting: false