LU-5070 utils: mkfs.lustre code cleanup

LU-5070 utils: mkfs.lustre code cleanup

Re-order the options to increase the code readability.
Remove unused code, redundant logic, white spaces,
blank lines, and so on.

Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: I88ee52fb2425e9e256b7751bad4b6cfcd88011ec
Reviewed-on: http://review.whamcloud.com/15303
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Ben Evans <bevans@cray.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>