Incorrect Error Check in function SSL_write()

[lc3412]

Hi,
Function SSL_write() returns the value of 0 and less than 0 are both on error. However , the return value of function SSL_write() is not checked correctly, which forgot to check the return value 0. See the following code:

line : 1098, 1101

trafficserver/tools/http_load/http_load.c

Lines 1097 to 1106 in 5ee6a5f

	if (urls[url_num].protocol == PROTO_HTTPS)
	r = SSL_write(connections[cnum].ssl, urls[url_num].buf, urls[url_num].buf_bytes);
	else
	r = write(connections[cnum].conn_fd, urls[url_num].buf, urls[url_num].buf_bytes);
	if (r < 0) {
	perror(urls[url_num].url_str);
	connections[cnum].reusable = 0;
	close_connection(cnum);
	return;
	}

The same situation is also occured on line 1216, 1219

trafficserver/tools/http_load/http_load.c

Lines 1215 to 1224 in 5ee6a5f

	if (urls[url_num].protocol == PROTO_HTTPS)
	r = SSL_write(connections[cnum].ssl, urls[url_num].buf, urls[url_num].buf_bytes);
	else
	r = write(connections[cnum].conn_fd, urls[url_num].buf, urls[url_num].buf_bytes);
	if (r < 0) {
	perror(urls[url_num].url_str);
	connections[cnum].reusable = 0;
	close_connection(cnum);
	return;
	}

===============================================================================

We find the return value of this call been checked in openssl project with the version of openssl 1.1.2.
Such as in openssl/apps folder

Ref : https://github.com/openssl/openssl/blob/0db957dbbcf6a432086ab913378c23636d8c374c/apps/s_time.c#L231-L232

line 231:     if (buf_len <= 0 || SSL_write(scon, buf, buf_len) <= 0)
line 232:         goto end;

Chi Li, Zuxing Gu, Jiecheng Wu

[bryancall]

Relates to #4293

[bryancall]

@lc3412 Can you please make a PR for this?