Add test whether optional `conn` is used
Add test whether optional `conn` is used

This is the test mentioned in one of the previous commits concerning
`fetch_user`s new `conn` kw-arg, which allows usage of an already
existing connection, instead of performing a system bind each time.

agdsn/sipa,MarauderXtreme/sipa,lukasjuhrich/sipa,lukasjuhrich/sipa,lukasjuhrich/sipa,MarauderXtreme/sipa,MarauderXtreme/sipa,lukasjuhrich/sipa,agdsn/sipa,agdsn/sipa,agdsn/sipa