LU-14385 utils: add range check to strtoul() in lfs.c

LU-14385 utils: add range check to strtoul() in lfs.c

Most of the strtoul() functions called in lfs.c
did not check the range of the return value.
This patch fixes those issues.

Change-Id: If1eb64750507b5fa4e22abe710e475e2f0032b4d
Signed-off-by: Jian Yu <yujian@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/41726
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: John L. Hammond <jhammond@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>