Regenerate sid when sbdy tries to fixate the session

Fixed broken test.

Thanks Stephen Richards for reporting.
Fix typo [ci skip]
Merge pull request #16393 from jonatack/patch-8

Fix typo [ci skip]
Only define Objetc#itself when it is not defined

Ruby 2.2 will include Kernel#itself so we don't need to define again.

See
https://github.com/ruby/ruby/commit/0a0160d6b659f6131a525fe1579e7c463d4c197e
[ci skip] Guides: Add definition of `config.assets.manifest` option to configuring.md
Merge pull request #16375 from johnnyshields/guides

Guides: Add definition of `config.assets.manifest` option to configuring.md
Update itself.rb [ci skip]
Merge pull request #16395 from jonatack/patch-8

Update itself.rb [ci skip]