Description of problem:

In one of the performance testing effort, we found that below options help improve the overall performance numbers of gluster-block workload:

performance.io-thread-count             16 -> 32
performance.high-prio-threads           16 -> 32
performance.normal-prio-threads         16 -> 32
performance.low-prio-threads            16 -> 32
performance.least-prio-threads          1  -> 4
client.event-threads                    2  -> 8
server.event-threads                    1  -> 8
performance.client-io-threads          off -> on


I was thinking its good idea to add this changes to current block profile, as we have data showing improvements in perf results.

Also, its good idea to re-validate the existing gluster-block profile options in  
/var/lib/glusterd/groups/gluster-block


PR: https://review.gluster.org/#/c/glusterfs/+/22963/