Make sure the permissions check file is closed before being unlinked.

[#1035 state:committed]

activesupport/lib/active_support/core_ext/file/atomic.rb

@@ -28,7 +28,7 @@ def atomic_write(file_name, temp_dir = Dir.tmpdir)
           rescue Errno::ENOENT
             # No old permissions, write a temp file to determine the defaults
             check_name = ".permissions_check.#{Thread.current.object_id}.#{Process.pid}.#{rand(1000000)}"
-            new(check_name, "w")
+            open(check_name, "w") { }
             old_stat = stat(check_name)
             unlink(check_name)
           end