Added test for a rare case to the host_alias-lib test
Added test for a rare case to the host_alias-lib test

The new tests now also cover the case of a malformed record type, which
wasn't covered before and which is very hard to create.
refs #395

agdsn/pycroft,agdsn/pycroft,lukasjuhrich/pycroft,agdsn/pycroft,agdsn/pycroft,lukasjuhrich/pycroft,lukasjuhrich/pycroft,lukasjuhrich/pycroft,agdsn/pycroft