polkitAuthenticationAgent.js: Ensure Cinnamon is part of the (#12887) correct login session when registering. Compare Cinnamon's session id with cinnamon-session's (which should never change), and have cinnamon-session restart us if there is a mismatch. Ref: #12669, #12728. See: https://github.com/linuxmint/cinnamon-session/pull/184.