GUACAMOLE-622: Ensure connection to guacd is kept alive even if the SSH daemon is taking its time responding. Lengthy connect times due to DNS verification, PAM, etc. are not uncommon.

src/protocols/ssh/ssh.c

@@ -233,6 +233,9 @@ void* ssh_client_thread(void* data) {
         return NULL;
     }
 
+    /* Ensure connection is kept alive during lengthy connects */
+    guac_socket_require_keep_alive(client->socket);
+
     /* Open SSH session */
     ssh_client->session = guac_common_ssh_create_session(client,
             settings->hostname, settings->port, ssh_client->user, settings->server_alive_interval,