Disable EDNS for the fetchlimit test server

The fetchlimit test depends on a resolver continuing to try UDP
and timing out while the client waits for resolution to succeed.
but since commit bb990030 (flag day 2020), a fetch will always
switch to TCP after two timeouts, unless EDNS was disabled for
the query.

This commit adds "edns no;" to server statements in the fetchlimit
resolver, to restore the behavior expected by the test.

(cherry picked from commit 81deb24deb)

bin/tests/system/fetchlimit/ns3/named1.conf.in

@@ -28,6 +28,10 @@ options {
 	fetches-per-server 400;
 };
 
+server 10.53.0.4 {
+	edns no;
+};
+
 key rndc_key {
 	secret "1234abcd8765";
 	algorithm hmac-sha256;

bin/tests/system/fetchlimit/ns3/named2.conf.in

@@ -26,6 +26,10 @@ options {
 	fetches-per-zone 40;
 };
 
+server 10.53.0.4 {
+	edns no;
+};
+
 key rndc_key {
 	secret "1234abcd8765";
 	algorithm hmac-sha256;

bin/tests/system/fetchlimit/ns3/named3.conf.in

@@ -26,6 +26,10 @@ options {
 	recursive-clients 400;
 };
 
+server 10.53.0.4 {
+	edns no;
+};
+
 key rndc_key {
 	secret "1234abcd8765";
 	algorithm hmac-sha256;