Update README.md

Added submodule update for warden-test-infrastructure instructions
recovered jobs continue discarding output

This fixes the case where a job was started and told to discard output,
and then Warden is drained and recovers from snapshots. Previously it
would start tracking output again, which could lead to 'output exceeded'
errors.
allow configuring pidfile to be written on startup

This pidfile will be written after the server boots up and is in a
functional state, i.e. all containers are recovered and it's started
listening on the socket.

[#57361124]
Change em-warden, warden client and warden proto so that it will work with a local connection with port on windows and not try to connnect to a unix domain.