Fix : NoneType error on user not found

Return "None" of function find_contact_entry was not managed and forced
the module to stop and lock all AD connections :
[WebUI] The mod ActiveDir_UI raise an exception: argument of type
'NoneType' is not iterable, I'm tagging it to restart later
Fix : Upper case False
Merge pull request #7 from cyrilleJ/master

Fix : NoneType error on user not found