Push notifications: Clean up logic for register/unregister tokens#16434

itsmeichigo merged 5 commits intotrunkwoocommerce/woocommerce-ios:trunkfrom

woomob-1851-ios-do-not-unregister-device-upon-store-switchingwoocommerce/woocommerce-ios:woomob-1851-ios-do-not-unregister-device-upon-store-switchingCopy head branch name to clipboard