Added FtpMonitor service success information

opennms-doc/guide-admin/src/asciidoc/text/poller/FtpMonitor.adoc

@@ -4,6 +4,25 @@
 The FtpMonitor is able to validate ftp connection dial-up processes.
 The monitor can test ftp server on multiple ports and specific login data.
 
+The service using the FtpMonitor is _up_ if the FTP server responds with error codes between 200 and 299.
+For special cases the service is also marked as _up_ for 425 and 530.
+
+[quote#Comment from FtpMonitor source]
+____
+ Also want to accept the following
+ ERROR message generated by some FTP servers
+ following a QUIT command without a previous
+ successful login:
+ 
+ "530 QUIT : User not logged in. Please login with
+ USER and PASS first."
+ 
+ Also want to accept the following ERROR
+ message generated by some FTP servers following a
+ QUIT command without a previously successful login:
+
+ "425 Session is disconnected."
+____
 
 ==== Monitor facts