REGTESTS: Don't try to use real nameservers for testcases

The test doesn't need a real nameserver and in a isolated, restricted
test environment it might not be able to reach one at all, like with a
network sandbox. So lets just use 127.0.0.1:53. Even if there is none,
that's not a problem for this particular test.

Signed-off-by: Christian Ruppert <idl0r@qasl.de>

reg-tests/server/cli_set_fqdn.vtc

@@ -42,7 +42,7 @@ haproxy h2 -conf {
         timeout server  "${HAPROXY_TEST_TIMEOUT-5s}"
 
     resolvers systemdns
-        parse-resolv-conf
+        nameserver dns1 127.0.0.1:53
 
     frontend myfrontend
         bind "fd@${my_fe}"