Move commands to the base testenv

This should allow py27 and py35 to both work in parallel while we remove
the run-tests versions.

Add the new jobs here, even though the next patch will remove them,
since we can't verify the new jobs work with depends-on to
project-config.

Change-Id: I78cfadf5a3b9822ce32f5a1d9b76321d573618ab

.zuul.yaml

@@ -27,9 +27,13 @@
         - devstack:
             files:
               - ^roles/
+        - openstack-tox-py27
+        - openstack-tox-py35
         - devstack-gate-tox-run-tests
         - devstack-gate-tox-py3-run-tests
     gate:
       jobs:
+        - openstack-tox-py27
+        - openstack-tox-py35
         - devstack-gate-tox-run-tests
         - devstack-gate-tox-py3-run-tests

tox.ini

@@ -6,17 +6,16 @@ skipsdist = True
 [testenv]
 install_command = pip install -U {opts} {packages}
 setenv = VIRTUAL_ENV={envdir}
-
-[testenv:run-tests]
 deps = -r{toxinidir}/test-requirements.txt
 commands =
   bash -c "./run-tests.sh"
 
+[testenv:run-tests]
+deps = -r{toxinidir}/test-requirements.txt
+
 [testenv:py3-run-tests]
 basepython = python3
 deps = -r{toxinidir}/test-requirements.txt
-commands =
-  bash -c "./run-tests.sh"
 
 [testenv:bashate]
 deps=