swim/join: add fixed backoff to retries on join
swim/join: add fixed backoff to retries on join

esatterwhite/skyring,uber-node/ringpop-node,hj3938/ringpop,hotrannam/ringpop,uber/ringpop-node,Collin-V/ringpop,uber-node/ringpop-node,uber/ringpop,tomasdiez/ringpop,esatterwhite/skyring,sasa233/ringpop,uber/ringpop-node