Add stestr master job

Tempest use stestr to run the tests, adding
a experimental and periodic job to run Tempest
with stestr master will help to detect any
breaking change in advance.

Change-Id: Ice57e193c5150be7141e0e003be5091a191b854c
diff --git a/zuul.d/project.yaml b/zuul.d/project.yaml
index b93a8b0..923a597 100644
--- a/zuul.d/project.yaml
+++ b/zuul.d/project.yaml
@@ -109,6 +109,7 @@
             irrelevant-files: *tempest-irrelevant-files
     experimental:
       jobs:
+        - tempest-stestr-master
         - tempest-cinder-v2-api:
             irrelevant-files: *tempest-irrelevant-files
         - tempest-all:
@@ -133,3 +134,4 @@
       jobs:
         - tempest-all
         - tempest-full-oslo-master
+        - tempest-stestr-master