Clear named routes when routes.rb is reloaded

Fix an issue where Journey was failing to clear the named routes hash when the
routes were reloaded and since it doesn't overwrite existing routes then if a
route changed but wasn't renamed it kept the old definition. This was being
masked by the optimised url helpers so it only became apparent when passing an
options hash to the url helper.

(cherry picked from commit e5275f9b5924f36f2bdd4dd9ac0a4f420384748f)

Conflicts:
	actionpack/CHANGELOG.md