Address feedback from igor and schleyfox

Adds a comment about when we write out the file output and restored
random backend ordering.

lib/synapse/file_output.rb

@@ -40,6 +40,9 @@ def write_backends_to_file(service_name, new_backends)
       end
 
       if old_backends == new_backends
+        # Prevent modifying the file unless something has actually changed
+        # This way clients can set watches on this file and update their
+        # internal state only when the smartstack state has actually changed
         return false
       else
         # Atomically write new sevice configuration file

lib/synapse/haproxy.rb

@@ -715,7 +715,8 @@ def generate_backend_stanza(watcher, config)
       stanza = [
         "\nbackend #{watcher.name}",
         config.map {|c| "\t#{c}"},
-        backends.map {|backend_name, backend|
+        backends.keys.shuffle.map {|backend_name|
+          backend = backends[backend_name]
           b = "\tserver #{backend_name} #{backend['host']}:#{backend['port']}"
           b = "#{b} cookie #{backend_name}" unless config.include?('mode tcp')
           b = "#{b} #{watcher.haproxy['server_options']}"