Remove if statements from `user_in_...` checks
Remove if statements from `user_in_...` checks

Return type of `in` is `bool`, so code only needs to return that
directly.

Also fix trailing whitespace and use present tense in function
docstrings to match others.

owncloud/pyocclient,blizzz/pyocclient,owncloud/pyocclient,blizzz/pyocclient