kex: docs - note that is_myself() does not match with default ports

(cherry picked from commit d2841c6)

src/modules/kex/doc/kex_admin.xml

@@ -350,7 +350,10 @@ pv_printf("$avp(x)", "From: $fU - To: $tU");
 		<title><function moreinfo="none">is_myself(uri)</function></title>
 		<para>
 			Check if the parameter matches the 'myself' condition (i.e., is
-			a local IP or domain).
+			a local IP or domain). Note that if the port is missing in the URI,
+			then no port matching is done (in other words, port matching is
+			skipped -- it does not use default SIP ports 5060 or 5061 for
+			matching).
 		</para>
 		<para>Meaning of the parameters is as follows:</para>
 		<itemizedlist>