LU-16386 mkfs: Handle --version argument correctly

LU-16386 mkfs: Handle --version argument correctly

Running mkfs.lustre with --version or -V argument
fails instead of printing the version. This patch
fixes the error.

Without patch:
--------------
$ ./lustre/utils/mkfs.lustre --version
usage: mkfs.lustre <target type> [--backfstype=ldiskfs]
<snip>

With patch:
-----------
$ ./lustre/utils/mkfs.lustre --version
mkfs.lustre 2.15.52_175_ge7aa83d

Test-Parameters: trivial fstype=zfs testlist=sanity
Signed-off-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Change-Id: I4d4d1144d669fce8b02e9f8c3fb5f45f68b337b4
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/49379
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>