Consume tox instead of zuul-tox

Change-Id: Ia31e642352c61dd4091570b54f566e02b6399800
Depends-On: I3fc7f89f4939fbcf82f329441d4b4693b80f6bc4

.zuul.yaml

@@ -2,8 +2,8 @@
     name: openstack-infra/zuul
     check:
       jobs:
-        - zuul-tox-docs
-        - zuul-tox-cover
-        - zuul-tox-linters
-        - zuul-tox-py35
-        - zuul-tox-tarball
+        - tox-docs
+        - tox-cover
+        - tox-linters
+        - tox-py35
+        - tox-tarball