[cdc_rsync] [cdc_stream] Remove SSH port argument (#41)

This CL removes the port arguments for both tools.

The port argument can also be specified via the ssh-command and
scp-command flags. In fact, if a port is specified by both port flags
and ssh/scp commands, they interfere with each other. For ssh, the one
specified in ssh-command wins. For scp, the one specified in
scp-command wins. To fix this, one would have to parse scp-command and
remove the port arg there. Or we could just remove the ssh-port arg.
This is what this CL does. Note that if you need a custom port, it's
very likely that you also have to define custom ssh and scp commands.

cdc_stream/session.cc

@@ -47,11 +47,11 @@ Session::Session(std::string instance_id, const SessionTarget& target,
       mount_dir_(target.mount_dir),
       cfg_(std::move(cfg)),
       process_factory_(process_factory),
-      remote_util_(cfg_.verbosity, cfg_.quiet, process_factory,
+      remote_util_(target.user_host, cfg_.verbosity, cfg_.quiet,
+                   process_factory,
                    /*forward_output_to_logging=*/true),
       metrics_recorder_(std::move(metrics_recorder)) {
   assert(metrics_recorder_);
-  remote_util_.SetUserHostAndPort(target.user_host, target.ssh_port);
   if (!target.ssh_command.empty()) {
     remote_util_.SetSshCommand(target.ssh_command);
   }