LU-2144 utils: reset 'optind' to avoid segmentation fault

LU-2144 utils: reset 'optind' to avoid segmentation fault

Sometimes lfsck_{start,stop} commands may be called several
times under the same lctl shell. Under such case, the function
getopt_long() called inside the lfsck_start/lfsck_stop may be
confused, and cause segmentation fault. So reset the external
variable 'optind' by force to avoid the segmentation fault.

Signed-off-by: Fan Yong <yong.fan@whamcloud.com>
Change-Id: I90c13226101af34948e45959b55752123e77fc9f
Reviewed-on: http://review.whamcloud.com/4251
Tested-by: Hudson
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>