Revert "Use VncAuth as the default security type, ..."

This reverts commit 39d7dc043afcf6f94b9c16942765fdb9a6a3202e.

We should be secure by default, even if it might cause a performance
hit. Those who wish to make that trade off are more likely to notice
the lack of performance than others noticing the lack of security.
diff --git a/common/rfb/SecurityServer.cxx b/common/rfb/SecurityServer.cxx
index 5bd7b2c..e0aee13 100644
--- a/common/rfb/SecurityServer.cxx
+++ b/common/rfb/SecurityServer.cxx
@@ -43,7 +43,7 @@
 #endif
  ")",
 #ifdef HAVE_GNUTLS
- "VncAuth,TLSVnc",
+ "TLSVnc,VncAuth",
 #else
  "VncAuth",
 #endif