Revert "Implement notifies for transfer plugin (#3972)" (#3995)

This reverts commit 68f1dd5ddf.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

plugin/secondary/README.md

@@ -24,16 +24,17 @@ A working syntax would be:
 ~~~
 secondary [zones...] {
     transfer from ADDRESS
+    transfer to ADDRESS
 }
 ~~~
 
 * `transfer from` specifies from which address to fetch the zone. It can be specified multiple times;
-    if one does not work, another will be tried. Transfering this zone outwards again can be done by
-    enableing the *transfer* plugin.
+    if one does not work, another will be tried.
+* `transfer to` can be enabled to allow this secondary zone to be transferred again.
 
 When a zone is due to be refreshed (Refresh timer fires) a random jitter of 5 seconds is
 applied, before fetching. In the case of retry this will be 2 seconds. If there are any errors
-during the transfer in, the transfer fails; this will be logged.
+during the transfer the transfer fails; this will be logged.
 
 ## Examples
 
@@ -42,7 +43,8 @@ Transfer `example.org` from 10.0.1.1, and if that fails try 10.1.2.1.
 ~~~ corefile
 example.org {
     secondary {
-        transfer from 10.0.1.1 10.1.2.1
+        transfer from 10.0.1.1
+        transfer from 10.1.2.1
     }
 }
 ~~~
@@ -50,12 +52,10 @@ example.org {
 Or re-export the retrieved zone to other secondaries.
 
 ~~~ corefile
-example.net {
-    secondary {
+. {
+    secondary example.net {
         transfer from 10.1.2.1
-    }
-    transfer {
-        to *
+        transfer to *
     }
 }
 ~~~
@@ -63,7 +63,3 @@ example.net {
 ## Bugs
 
 Only AXFR is supported and the retrieved zone is not committed to disk.
-
-## Also See
-
-See the *transfer* plugin to enable zone transfers _to_ other servers.