Don't run kolla functional gate as root

Because of a recent change, docker image building cannot be done
as the root user.  This is a good thing ;)  But breaks the current
gate.

Also we have a setup_docker.sh script already in our tools directory,
so rename the script we are running to setup_gate.sh because that is
actually what the script does.

Change-Id: I8f86616fb19b4b03f34fe40acf1689f6b174ff98

jenkins/jobs/kolla.yaml

@@ -13,8 +13,8 @@
       - gerrit-git-prep
       - shell: |
           #!/bin/bash -xe
-          sudo tests/setup_docker.sh
-          sudo tox -e images
+          tests/setup_gate.sh
+          tox -e images
 
     publishers:
       - console-log