check_smtp.c: modified SSL check for use with -e

  - currently STARTTLS check does not work with -e if there's text
    like '220 hostname ESMTP*'. This is caused by SMTP answer from
    host. Postfix answer: 220 2.0.0 Ready to start TLS, Exchange
    2010: 220 2.0.0 SMTP server ready. This fix checks against 220

    closes #1093

plugins/check_smtp.c

@@ -231,7 +231,7 @@ main (int argc, char **argv)
 		  send(sd, SMTP_STARTTLS, strlen(SMTP_STARTTLS), 0);
 
 		  recvlines(buffer, MAX_INPUT_BUFFER); /* wait for it */
-		  if (!strstr (buffer, server_expect)) {
+		  if (!strstr (buffer, SMTP_EXPECT)) {
 		    printf (_("Server does not support STARTTLS\n"));
 		    smtp_quit();
 		    return STATE_UNKNOWN;