Switch to get_once for consistency

Author: HD Moore

modules/exploits/windows/smtp/ms03_046_exchange2000_xexch50.rb

@@ -151,7 +151,7 @@ def exploit
 
         sock.put("XEXCH50 2 2\r\n")
         select(nil,nil,nil,3)
-        res = sock.get(-1,3)
+        res = sock.get_once
         print_status("#{res}")
         if (res !~ /Send binary data/)
           print_status("Target is not vulnerable.")