nathelper: update flag documenation

(cherry picked from commit 95fa98e)

src/modules/nathelper/doc/nathelper_admin.xml

@@ -173,13 +173,13 @@ modparam("nathelper", "natping_interval", 10)
 		<title><varname>ping_nated_only</varname> (integer)</title>
 		<para>
 		If this parameter is set to 1 then only contacts that have
-		<quote>behind_NAT</quote> flag in user location database set will
-		get ping.
+		the behind NAT <quote>nat_bflag</quote> flag in user location
+		database set will get ping.
 		</para>
 		<para>
-		If it is 0 and sipping_flag is not set, then the 4-bytes UDP ping is
-		sent to all contacts. If it is 0 and sipping_flag parameter is set, then
-		SIP-request-based pinging is sent to all contacts.
+		If it is 0 and sipping_bflag is not set, then the 4-bytes UDP ping
+		is sent to all contacts. If it is 0 and sipping_bflag parameter
+		is set, then SIP-request-based pinging is sent to all contacts.
 		</para>
 		<para>
 		<emphasis>