Relocate branch conditional for tempest-full job

This condition was added to openstack-zuul-jobs in [1], but it created
bug #1739829 as a side effect. While addressing the issue [2] it was
noticed  that conditional could be located in the tempest repo itself,
so this patch aims at cleaning things up a bit and reduce the moving
parts.

[1] I799ea86f3c445bb067950a8cbc237999d621e3a9
[2] I5d34e5b983b720dc1913d00ccc1a16d81a040d49
Needed-by: Ibfbc925af6eb274ced53312301b1733136ba4455
Partial-bug: #1739829

Change-Id: I8e0aa11cd2d92d5d6f5e9147a407374948920e7f
diff --git a/.zuul.yaml b/.zuul.yaml
index 10788d7..f615447 100644
--- a/.zuul.yaml
+++ b/.zuul.yaml
@@ -17,7 +17,10 @@
     name: tempest-full
     parent: devstack-tempest
     # This currently only works on the master branch.
-    branches: master
+    # NOTE(andreaf) Only run on master for now.
+    # The negative lookup is redudant but it's a
+    # reminder that we don't want the job running there.
+    branches: ^(?!driverfixes/)master$
     description: |
       Base integration test with Neutron networking and py27.
       Former names for this job where: