Clean up shebangs for various files.

- Remove shebangs from:
  - ini files
  - unit tests
  - module_utils
  - plugins
  - module_docs_fragments
  - non-executable Makefiles
- Change non-modules from '/usr/bin/python' to '/usr/bin/env python'.
- Change '/bin/env' to '/usr/bin/env'.

Also removed main functions from unit tests (since they no longer
have a shebang) and fixed a python 3 compatibility issue with
update_bundled.py so it does not need to specify a python 2 shebang.

A script was added to check for unexpected shebangs in files.
This script is run during CI on Shippable.

hacking/update_bundled.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python2 -tt
+#!/usr/bin/env python
 
 import glob
 import json
@@ -25,7 +25,7 @@ for filename in glob.glob(os.path.join(basedir, '../lib/ansible/compat/*/__init_
             continue
         metadata = json.loads(data)
         pypi_fh = open_url('https://pypi.python.org/pypi/{0}/json'.format(metadata['pypi_name']))
-        pypi_data = json.loads(pypi_fh.read())
+        pypi_data = json.loads(pypi_fh.read().decode('utf-8'))
         if LooseVersion(metadata['version']) < LooseVersion(pypi_data['info']['version']):
             print('UPDATE: {0} from {1} to {2} {3}'.format(
                 metadata['pypi_name'],