Run functions implemented by this worker
Connect to a given worker, returning a type wrapped Rpc.Connection.t that can be
used to run functions.
with_client worker init_arg f connects to the worker's server, initializes the
connection state with init_arg and runs f until an exception is thrown or
until the returned Deferred is determined.
NOTE: You should be careful when using this with Pipe_rpc.
See Rpc.Connection.with_close for more information.