LU-14265 utils: allow 'lfs mkdir' without arguments

LU-14265 utils: allow 'lfs mkdir' without arguments

If no arguments are given to "lfs mkdir <newdir>" assume that
"-i -1 -c 1" were given, to create the specified <newdir> on
an MDT with above-average free space/inodes.

Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: I319f68240832a905a86833a70a4631cde5ce7057
Reviewed-on: https://review.whamcloud.com/41054
Reviewed-by: Olaf Faaland-LLNL <faaland1@llnl.gov>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Lai Siyao <lai.siyao@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>