ShardedTP: The config option changed
The config option for sharded threadpool is changed to
osd_op_num_threads_per_shard instead of osd_op_num_sharded_pool_threads.
Along with osd_op_num_shards this will be much more user friendly while
configuring the number of op threads for the osd.

Signed-off-by: Somnath Roy <somnath.roy@sandisk.com>