Fix a possible excessive memory use issue in controller and clean up a bunch of COM handling and other code in the normal node.

node/Constants.hpp

@@ -539,6 +539,11 @@
  */
 #define ZT_PEER_CREDENTIALS_CUTOFF_LIMIT 15
 
+/**
+ * Rate limit for responding to peer credential requests
+ */
+#define ZT_PEER_CREDENTIALS_REQUEST_RATE_LIMIT 1000
+
 /**
  * WHOIS rate limit (we allow these to be pretty fast)
  */