Adding additional options for os_workers.rb:
os_workers_small
os_workers_large
os_workers will provide response times close to what
$::processorcount had (with two sockets machines).
os_workers_small will be the existing calculation.
os_workers_large can be used where services are distributed across
multiple machines and high worker count is not a concern.
Closes-bug: #1650424
Change-Id: I5dce760044d49ef9e3c88736c73cc267fd039ae7