Run octavia-tempest-plugin against stable/stein

This patch adds two new gate jobs that run octavia-tempest-plugin tests
against stable/stein.

Change-Id: Ia7dc937ebab0ba743f04fbf6d26b634fe90ab843
diff --git a/zuul.d/projects.yaml b/zuul.d/projects.yaml
index 07ec7ff..387f123 100644
--- a/zuul.d/projects.yaml
+++ b/zuul.d/projects.yaml
@@ -9,10 +9,12 @@
       jobs:
         - octavia-v2-dsvm-noop-api
         - octavia-v2-dsvm-noop-py2-api
+        - octavia-v2-dsvm-noop-api-stable-stein
         - octavia-v2-dsvm-noop-py2-api-stable-rocky
         - octavia-v2-dsvm-noop-py2-api-stable-queens
         - octavia-v2-dsvm-scenario
         - octavia-v2-dsvm-py2-scenario
+        - octavia-v2-dsvm-scenario-stable-stein
         - octavia-v2-dsvm-py2-scenario-stable-rocky
         - octavia-v2-dsvm-py2-scenario-stable-queens
         - octavia-v2-dsvm-scenario-centos-7:
@@ -30,9 +32,11 @@
       jobs:
         - octavia-v2-dsvm-noop-api
         - octavia-v2-dsvm-noop-py2-api
+        - octavia-v2-dsvm-noop-api-stable-stein
         - octavia-v2-dsvm-noop-py2-api-stable-rocky
         - octavia-v2-dsvm-noop-py2-api-stable-queens
         - octavia-v2-dsvm-scenario
         - octavia-v2-dsvm-py2-scenario
+        - octavia-v2-dsvm-scenario-stable-stein
         - octavia-v2-dsvm-py2-scenario-stable-rocky
         - octavia-v2-dsvm-py2-scenario-stable-queens