squash w/ [?] Fix error handling logic for heartbeat operation.

server/main_server/src/agent_main.cpp

@@ -832,6 +832,10 @@ namespace
 
             while (bytes_to_send) {
                 const int bytes_sent = send(net_obj->socket_handle(), &(heartbeat[heartbeat_length - bytes_to_send]), bytes_to_send, 0);
+
+                // We do not check for 0 because it is not considered an error condition. It only means 0
+                // bytes were sent. As longs as we have more bytes to send and no error has occurred, we
+                // keep attempting to send bytes.
                 if (bytes_sent == -1) {
                     const int errsav = errno;
                     if (errsav != EINTR) {