[sshsession] Enable NODELAY

Enable NODELAY by default our ssh usage, which include interactive
console clients and and sftp server, benefit greatly in terms of
performance.

Fixes canonical#167.

src/ssh/ssh_session.cpp

@@ -93,12 +93,14 @@ mp::SSHSession::SSHSession(const std::string& host, int port, const SSHKeyProvid
     if (session == nullptr)
         throw std::runtime_error("Could not allocate ssh session");
 
-    const long timeout = 1;
+    const long timeout{1};
+    const int nodelay{1};
 
     SSH::throw_on_error(ssh_options_set, session, SSH_OPTIONS_HOST, host.c_str());
     SSH::throw_on_error(ssh_options_set, session, SSH_OPTIONS_PORT, &port);
     SSH::throw_on_error(ssh_options_set, session, SSH_OPTIONS_USER, "ubuntu");
     SSH::throw_on_error(ssh_options_set, session, SSH_OPTIONS_TIMEOUT, &timeout);
+    SSH::throw_on_error(ssh_options_set, session, SSH_OPTIONS_NODELAY, &nodelay);
     SSH::throw_on_error(ssh_connect, session);
     if (key_provider)
         SSH::throw_on_error(ssh_userauth_publickey, session, nullptr, key_provider->private_key());