LU-4063 tests: use $DIR to check file at agent host

LU-4063 tests: use $DIR to check file at agent host

12a used to use DIR2 which is not mounted at agent host.

Lustre-change: http://review.whamcloud.com/#/c/7869/
Lustre-commit: f0f0a4951493859d213ae41b7818722e7c37e58a

Change-Id: Icad9a478700f4365d80233515931f9be28a78332
Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-on: http://review.whamcloud.com/9860
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Faccini Bruno <bruno.faccini@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>