Make Launcher#close_binder_listeners public

To avoid a `send` call in `cluster.rb` and to indicate to the maintainers that other classes use this method, we will make it public.

lib/puma/cluster.rb

@@ -411,7 +411,7 @@ def setup_signals
           log "Early termination of worker"
           exit! 0
         else
-          @launcher.send(:close_binder_listeners)
+          @launcher.close_binder_listeners
 
           stop_workers
           stop

lib/puma/launcher.rb

@@ -214,6 +214,15 @@ def restart_args
       end
     end
 
+    def close_binder_listeners
+      @binder.listeners.each do |l, io|
+        io.close
+        uri = URI.parse(l)
+        next unless uri.scheme == 'unix'
+        File.unlink("#{uri.host}#{uri.path}")
+      end
+    end
+
     private
 
     def reload_worker_directory
@@ -319,16 +328,6 @@ def prune_bundler?
       @options[:prune_bundler] && clustered? && !@options[:preload_app]
     end
 
-    def close_binder_listeners
-      @binder.listeners.each do |l, io|
-        io.close
-        uri = URI.parse(l)
-        next unless uri.scheme == 'unix'
-        File.unlink("#{uri.host}#{uri.path}")
-      end
-    end
-
-
     def generate_restart_data
       if dir = @options[:directory]
         @restart_dir = dir