proxy -D option doesn't do anything useful

[rade]

I might be missing something here... but it seems to me that the -D proxy option, which configures how the proxy connects to Docker, doesn't do anything useful. The remote execution of the weave script with weavexec expects to talk to docker on the unix socket - it volume mounts the socket in exec_remote and when starting weave infrastructure containers.

If true, I suggest we get rid of the option from the docs (on latest_release_doc_updates, since we've had at least one user wasting hours because they misunderstood what -D was doing), and in the code.