LU-960 utils: bad stripe count report, and validate stripe size

LU-960 utils: bad stripe count report, and validate stripe size

Need to use %d to print -1 instead of %u
Need to check for -1 in input for stripe size

Signed-off-by: Minh Diep <mdiep@whamcloud.com>
Change-Id: Ic4ee84a45bdb5dc934a3e681a4fc2fcd51f14b99
Reviewed-on: http://review.whamcloud.com/2112
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Cliff White <cliffw@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>