LU-3787 test: Missing "$" on variable

LU-3787 test: Missing "$" on variable

In test 90 of replay-single, the argument of
getstripe is $dir/file when it really should be
$dir/$file. Getstripe fails since "file" does
not exist.

The patch adds the "$" to the argument of getstripe.

Signed-off-by: James Nunez <james.a.nunez@intel.com>
Change-Id: I253c358d2912b57b54024f02a0a1ca54094369a7
Reviewed-on: http://review.whamcloud.com/7403
Tested-by: Hudson
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>