Both the plugin hooks and Mailer were setting default_url_options incorrectly
and causing ActionContoller::UrlWritter to cache the settings on the module
(mattr_accessor) causing several url generators to fail in either the plugin
hooks or the Mailer.
* Replaced Mailer's use of the default_url_options accessor with the proper class method
* Replaced Hook's use of the default_url_options accessor with the proper class method on the ViewListener class
* Added a test to reproduce the bugs in the Mailer when a hook is registered (thanks Chaoqun Zou)
#2542
