Table mapping for be_users and be_groups

[vnc-jboe]

The table mapping for be_users and be_groups is not correct.

If you want to set the receiver mails to a specific backend group, it does not work.

I already wrote a fix and made a pull request.

#1035

[vnc-jboe]

@mschwemer Could you take care of the fix?

A client needs this functionality and we would not like to write a patch.

[mschwemer]

Thanks for your contribution. Merged your PR,