LU-11045 test: use provided directory in racer/racer.sh

LU-11045 test: use provided directory in racer/racer.sh

In racer/racer.sh use the directory provided by the parent script
rather than the environmental variable $DIR.

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Change-Id: Iab753c34752462a30e7263b7c304e1626e5cc343
Reviewed-on: https://review.whamcloud.com/32514
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: James Nunez <jnunez@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>