stat: Print one-line iops stat

stat: Print one-line iops stat

This adds basic iops statistics (likewise to what we already have for
bandwidth) to normal and json fio output. Example for normal output:

   bw (  KiB/s): min=42192, max=162068, per=0.10%, avg=93236.21, stdev=22180.02
   iops : min=21090, max=81020, avg=46606.84, stdev=11088.40
    lat (usec) : 2=55.13%, 4=21.11%, 10=0.36%, 20=0.03%, 50=23.14%

Added handling for iops_stat to client/server and bump server version.

Signed-off-by: Andreas Herrmann <aherrmann@suse.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>