Add a specific trusty platform job

In If05224a2d5d880a2affc8d0f2ed5e0b8f554f022 we found that the
"updown" test was still running on trusty unintentionally.  Add a
specific platform job to keep the lights on for Ubuntu Trusty on the
devstack master branch.

Change-Id: I3d550af8ba57f2bec022901abdcc96024f5bc079

jenkins/jobs/projects.yaml

@@ -3841,6 +3841,12 @@
           job-suffix: '-nv'
           node: fedora-24
           neutron: 1
+      - '{pipeline}-tempest-dsvm-platform-{name}{job-suffix}':
+          pipeline: gate
+          name: ubuntu-trusty
+          job-suffix: ''
+          node: ubuntu-trusty
+          neutron: 1
 
 - project:
     name: devstack-plugin-additional-pkg-repos

zuul/layout.yaml

@@ -1214,6 +1214,10 @@ jobs:
   - name: ^gate-dib-dsvm-functests-ubuntu-trusty.*$
     branch: master
 
+  # This job keeps the lights on for Trusty on devstack master branch
+  - name: ^gate-tempest-dsvm-platform-ubuntu-trusty.*$
+    branch: master
+
   - name: ^gate-logstash-filters-ubuntu-(trusty|xenial)$
     voting: false
 
@@ -3567,6 +3571,7 @@ projects:
       - gate-grenade-dsvm-multinode
       - gate-grenade-dsvm-neutron-multinode-ubuntu-trusty
       - gate-grenade-dsvm-neutron-multinode-ubuntu-xenial
+      - gate-tempest-dsvm-platform-ubuntu-trusty
       - gate-tempest-dsvm-platform-centos7-nv
       - gate-tempest-dsvm-platform-fedora24-nv
     gate: