[beeswax] Fix test_save_results_to_dir to deal with hive tmp directories

The fix in https://github.com/cloudera/hue/commit/10430d14bcd64e93133d061e42c49a3d440b051b created a backwards incompatibility with lower versions of hive. This patch changes this to a more elegant fix that will maintain backwards compatibility with hive 1 by removing temporary files when it is listing from a directory.