LU-1075 tests: auster detect directory as script name

LU-1075 tests: auster detect directory as script name

Auster should use -f or detect the existing of script name
rather use -e which will treat directorysame as script.
Also, the patch of LU-412 is included to fix test script
lookup in auster.

port of master patch 0a79b541ad736bb296ea051e58b667c6195731a1
port of master patch 39b98cb351866da5648ea1a2216c108f8791226f

Signed-off-by: Minh Diep <mdiep@whamcloud.com>
Signed-off-by: Li Wei <liwei@whamcloud.com>
Signed-off-by: Liu Ying <emoly.liu@intel.com>
Change-Id: Id7d526b73051124b8b76deca974345573c6faf2b
Reviewed-on: http://review.whamcloud.com/4895
Tested-by: Hudson
Reviewed-by: Jian Yu <jian.yu@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Li Wei <wei.g.li@intel.com>
Reviewed-by: Johann Lombardi <johann.lombardi@intel.com>