Disable dnssec processing by default, as there are many open bugs in 4.0.0-alpha2 in that area.

See https://github.com/PowerDNS/pdns/pull/3529/files.

Index: pdns-recursor/pdns_recursor.cc
===================================================================
--- pdns-recursor.orig/pdns_recursor.cc
+++ pdns-recursor/pdns_recursor.cc
@@ -2624,7 +2624,7 @@ int main(int argc, char **argv)
     ::arg().set("local-address","IP addresses to listen on, separated by spaces or commas. Also accepts ports.")="127.0.0.1";
     ::arg().setSwitch("non-local-bind", "Enable binding to non-local addresses by using FREEBIND / BINDANY socket options")="no";
     ::arg().set("trace","if we should output heaps of logging. set to 'fail' to only log failing domains")="off";
-    ::arg().set("dnssec", "DNSSEC mode: off/process (default)/log-fail/validate")="process";
+    ::arg().set("dnssec", "DNSSEC mode: off/process (default)/log-fail/validate")="off";
     ::arg().set("daemon","Operate as a daemon")="no";
     ::arg().setSwitch("write-pid","Write a PID file")="yes";
     ::arg().set("loglevel","Amount of logging. Higher is more. Do not set below 3")="4";
