As per comments here #14691 and current comments on code here https://github.com/docker/docker/blob/master/daemon/start.go#L30 we could actually deprecate passing hostConfig to container start for newer api (> 1.21)

• close ReadOnlyRootfs only recognized when passed in containers/create #10695

ping @icecrime @cpuguy83 @LK4D4