issue 2287 - fixing user pass install not working

TempFiles are deleted at garbage collection time
http://www.ruby-doc.org/stdlib-1.9.3/libdoc/tempfile/rdoc/Tempfile.html

Previously we would simply return the path, discarding
the file object, so as soon as the create_temp_config_file
function returned, the file may be deleted.  Now we keep
track of the file object through the life of katello-configure