Disable auto discovery

Change in setuptools after latest release of setuptools 61.0
with breaking changes which are not backwork compatible,
details in related bug and [1].

Users that don't set ``packages``, ``py_modules``, or ``configuration`` are
still likely to observe the auto-discovery behavior, which may halt the
build if the project contains multiple directories and/or multiple Python
files directly under the project root.

To disable auto discovery, one can do below in setup.py

~~~
setuptools.setup(..,packages=[],..)
~~~

or

~~~
setuptools.setup(..,py_modules=[],..)
~~~

[1] https://github.com/pypa/setuptools/issues/3197

Change-Id: Ia544d7d82c0569c453f7cb75885b903d2e3cf83f

setup.py

@@ -18,4 +18,5 @@ import setuptools
 
 setuptools.setup(
     setup_requires=['pbr>=2.0.0'],
+    py_modules=[],
     pbr=True)