[doc] zebra.8 via Christian Hammers (#531)

The man page for zebra(8) mentions as port number to connect to 2602,
but it's acutally 2601 (as shown in /etc/services). 2602 belongs to ripd.
Attached patch fixes this typo.
diff --git a/doc/zebra.8 b/doc/zebra.8
index 9399be0..23703e7 100644
--- a/doc/zebra.8
+++ b/doc/zebra.8
@@ -62,7 +62,7 @@
 .TP
 \fB\-P\fR, \fB\-\-vty_port \fR\fIport-number\fR 
 Specify the port that the zebra VTY will listen on. This defaults to
-2602, as specified in \fB\fI/etc/services\fR.
+2601, as specified in \fB\fI/etc/services\fR.
 .TP
 \fB\-A\fR, \fB\-\-vty_addr \fR\fIvty-address\fR
 Specify the address that the zebra VTY will listen on. Default is all