Fix bug setting database user


git-svn-id: svn+ssh://svn.gna.org/svn/gnustep/libs/sqlclient/trunk@38070 72102866-910b-0410-8b05-ffd578937521
only disconnect when connected


git-svn-id: svn+ssh://svn.gna.org/svn/gnustep/libs/sqlclient/trunk@38071 72102866-910b-0410-8b05-ffd578937521