Add plugin to PROJECTS in keystone jobs

We forgot to add the keystone-tempest-plugin project to the PROJECTS
list so the keystone v3 nonvoting jobs are failing with "Invalid
requirement: '/opt/stack/new/keystone-tempest-plugin'".

Change-Id: I727866d4aa8ad3ef8962752dacce3a0e37d1ac01

jenkins/jobs/keystone.yaml

@@ -54,6 +54,7 @@
       - shell: |
           #!/bin/bash -xe
           export PYTHONUNBUFFERED=true
+          export PROJECTS="openstack/keystone-tempest-plugin $PROJECTS"
           export DEVSTACK_GATE_TEMPEST=1
           export BRANCH_OVERRIDE={branch-override}
           if [ "$BRANCH_OVERRIDE" != "default" ] ; then
@@ -93,6 +94,7 @@
           #!/bin/bash -xe
           export DEVSTACK_GATE_USE_PYTHON3=True
           export PYTHONUNBUFFERED=true
+          export PROJECTS="openstack/keystone-tempest-plugin $PROJECTS"
           export DEVSTACK_GATE_TEMPEST=1
 
           # swift is not ready for python3 yet