LU-13417 utils: lfs setdirstripe -D -i -1 should work

LU-13417 utils: lfs setdirstripe -D -i -1 should work

Allow "lfs setdirstripe -D -i -1" to work as expected to create remote
directories balanced across MDTs.  Otherwise, this sets a default
stripe count of 0, which results in only local directories created.

Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: I8fb92e352d278b0c2985976df69751309fce7057
Reviewed-on: https://review.whamcloud.com/38160
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Lai Siyao <lai.siyao@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>