setup.py: override modules to stop auto-detection

Some of our jobs have started failing with

   error: Multiple top-level packages discovered in a flat-layout:
   ['roles', 'playbooks'].
   ... <and so on> ...

which seems to be a combination of jobs that don't run often and some
recent-ish version of setuptools/pip.  From what I can tell, what we
want to do here is disable autodetection as what we have isn't really
a python distributable package.

Also fix the two places this is monkey-patched in over the existing
file.

Change-Id: I2a0dfbbedbb9bddd34b6af691118cf7c422a82b0

setup.py

@@ -25,4 +25,7 @@ except ImportError:
 
 setuptools.setup(
     setup_requires=['pbr>=2.0'],
-    pbr=True)
+    pbr=True,
+    # Override this to avoid trying to autodetect modules for
+    # packaging, as some roles have .py files
+    py_modules=[])

test-playbooks/python/fetch-subunit-output.yaml

@@ -25,7 +25,7 @@
           dest: tox.ini
         - content: |
             import setuptools
-            setuptools.setup()
+            setuptools.setup(py_modules=[])
           dest: setup.py
         - content: ""
           dest: setup.cfg

test-playbooks/python/fetch-tox-output.yaml

@@ -19,7 +19,7 @@
           dest: tox.ini
         - content: |
             import setuptools
-            setuptools.setup()
+            setuptools.setup(py_modules=[])
           dest: setup.py
         - content: ""
           dest: setup.cfg