* pip: combine chdir and env only when env is set
This fixes an AttributeError when chdir without virtualenv is specified:
File "/tmp/ansible_2UAFsZ/ansible_module_pip.py", line 387, in main
env = os.path.join(chdir, env)
File "/usr/lib64/python2.7/posixpath.py", line 75, in join
if b.startswith('/'):
AttributeError: 'NoneType' object has no attribute 'startswith'
* Add test for pip with chdir
Signed-off-by: Till Maas <opensource@till.name>
