ctdb-doc: Document that "ctdb tickle" can now read from stdin

BUG: https://bugzilla.samba.org/show_bug.cgi?id=12123

Although this has been queued for a while, with changes to add stdin
support to the original ctdb tool, this came for free with the
replacement tool.

addtickle and deltickle also now have this feature.  However, they're
internal commands and we're not adding new documentation for
internal/debug commands.

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>
(cherry picked from commit 2295f5009dabfc09eec40bb4f30679d76310ce12)

ctdb/doc/ctdb.1.xml

@@ -1440,13 +1440,24 @@ RUNNING
     </refsect2>
 
     <refsect2>
-      <title>tickle <parameter>SRC-IPADDR</parameter>:<parameter>SRC-PORT</parameter> <parameter>DST-IPADDR</parameter>:<parameter>DST-PORT</parameter></title>
+      <title>tickle</title>
       <para>
-	Send a TCP tickle to the source host for the specified TCP
-	connection.  A TCP tickle is a TCP ACK packet with an invalid
-	sequence and acknowledge number and will when received by the
-	source host result in it sending an immediate correct ACK back
-	to the other end.
+	Read a list of TCP connections, one per line, from standard
+	input and send a TCP tickle to the source host for each
+	connection.  A connection is specified as:
+      </para>
+      <synopsis>
+	<parameter>SRC-IPADDR</parameter>:<parameter>SRC-PORT</parameter> <parameter>DST-IPADDR</parameter>:<parameter>DST-PORT</parameter>
+      </synopsis>
+      <para>
+	A single connection can be specified on the command-line
+	rather than on standard input.
+      </para>
+      <para>
+	A TCP tickle is a TCP ACK packet with an invalid sequence and
+	acknowledge number and will when received by the source host
+	result in it sending an immediate correct ACK back to the
+	other end.
       </para>
       <para>
 	TCP tickles are useful to "tickle" clients after a IP failover has