Test case and fix for shlex.split unicode bug

When operating on a unicode string in python 2.6, shlex.split returns
a result that does not work with the file constructor.

To reproduce this requires a task include that is templated (this is
because the templated string is a unicode result, whereas a non-
templated string is a non-unicode string)

    [will@centos6.3] $ python
    Python 2.6.6 (r266:84292, Sep 11 2012, 08:34:23)
    [GCC 4.4.6 20120305 (Red Hat 4.4.6-4)] on linux2
    Type "help", "copyright", "credits" or "license" for more information.
    >>> import shlex
    >>> shlex.split(u'abc')
    ['a\x00\x00\x00b\x00\x00\x00c\x00\x00\x00']

    [will@fedora17] $ python
    Python 2.7.3 (default, Jul 24 2012, 10:05:38)
    [GCC 4.7.0 20120507 (Red Hat 4.7.0-5)] on linux2
    Type "help", "copyright", "credits" or "license" for more information.
    >>> import shlex
    >>> shlex.split(u'abc')
    ['abc']

The proposed fix (coercing the include parameters to string before the
shlex.split) may not be ideal but it does fix the bug for my test case.

lib/ansible/playbook/play.py

@@ -194,7 +194,7 @@ class Play(object):
                 task_vars['_original_file'] = original_file
 
             if 'include' in x:
-                tokens = shlex.split(x['include'])
+                tokens = shlex.split(str(x['include']))
                 items = ['']
                 included_additional_conditions = list(additional_conditions)
                 for k in x: