[ruby/fileutils] Skip test_cp_r_socket on JRuby

https://github.com/ruby/fileutils/commit/20bb9ec789

test/fileutils/test_fileutils.rb

@@ -461,6 +461,7 @@ class TestFileUtils < Test::Unit::TestCase
   rescue LoadError
   else
     def test_cp_r_socket
+      skip "Skipping socket test on JRuby" if RUBY_ENGINE == 'jruby'
       Dir.mkdir('tmp/cpr_src')
       UNIXServer.new('tmp/cpr_src/socket').close
       cp_r 'tmp/cpr_src', 'tmp/cpr_dest'