(#511) Reduce logging in network loops

Upcoming NATS broker will be significantly faster and so add a lot more
strain on these 2 code paths

Removing the log lines let it work unbatched for smallisy payload on 50k
nodes but really there's only so far this will go and we're getting
there now

lib/mcollective/connector/nats.rb

@@ -359,10 +359,10 @@ def receive
         msg = nil
 
         until msg
-          Log.debug("Waiting for a message from NATS")
-
           received = connection.receive
 
+          Thread.pass
+
           begin
             msg = JSON.parse(received)
           rescue

lib/mcollective/util/natswrapper.rb

@@ -210,8 +210,7 @@ def subscribe(source_name, options={})
           Log.debug("Subscribing to %s" % source_name)
 
           unless @subscriptions.include?(source_name)
-            @subscriptions[source_name] = @client.subscribe(source_name, options) do |msg, _, sub|
-              Log.debug("Received a message on %s" % [sub])
+            @subscriptions[source_name] = @client.subscribe(source_name, options) do |msg, _, _|
               @received_queue << msg
             end
           end