LU-6142 tests: Fix style issues for directio.c

This patch fixes issues reported by checkpatch
for file lustre/tests/directio.c

Test-Parameters: trivial
Signed-off-by: Arshad Hussain <arshad.super@gmail.com>
Change-Id: Ic1b39dd84aaef75c4bd94c357b6f917b735175cb
Reviewed-on: https://review.whamcloud.com/35816
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Shaun Tancheff <stancheff@cray.com>
Reviewed-by: Petros Koutoupis <pkoutoupis@cray.com>
Reviewed-by: Ben Evans <bevans@cray.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>