Refactors after_cancel to allow the Mailer method to follow the pattern set in other models.
Refactors after_cancel to allow the Mailer method to follow the pattern set in other models.

Allows OrderMailer.cancel_email be sent asynchronously with delayed_job#handel_aynchronously

Fixes #3759

Antdesk/karpal-spree,Antdesk/karpal-spree,Antdesk/karpal-spree