This PS increases the number of default RPC works to a more
sane value - even with a large number of replicas a single worker
thread has difficulty keeping up.
Change-Id: I9a4ce7a88983b52c506b6a5f6253688f8a3aa61e
Depends-On: I705f2ddf3facfe56838f606f88cfb15b822d18a5
Signed-off-by: Pete Birley <pete@port.direct>