Use all? method to check exclusive parameters

Signed-off-by: Hiroshi Hatake <[email protected]>

Author: cosmo0920

lib/fluent/plugin/filter_concat.rb

@@ -68,7 +68,7 @@ def configure(conf)
       super
 
       params, names = required_params
-      if params.reject{|e| e == true}.empty?
+      if params.all?
         raise Fluent::ConfigError, "Either #{[names[0..-2].join(", "), names[-1]].join(" or ")} is required"
       end
       if @n_lines && (@multiline_start_regexp || @multiline_end_regexp)