Small reset tweak in auth controller

It's clearer if the form clears itself through a reset rather than
waiting for it to happen later. This has the advantage of getting
the password out of reachable memory sooner.

Extending the scope rather than erasing its keys and replacing it
with the base scope means the Auth controller can clear the form
fields without clearing the session data in the scope.

h/js/controllers.coffee

@@ -629,7 +629,7 @@ class Auth
       code: null
 
     _reset = ->
-      angular.copy base, $scope.model
+      angular.extend $scope.model, base
       for own _, ctrl of $scope when typeof ctrl?.$setPristine is 'function'
         ctrl.$setPristine()
 
@@ -646,7 +646,7 @@ class Auth
       return unless form.$valid
       promise = session["$#{form.$name}"] ->
         $scope.$emit 'success', form.$name
-      promise.then(angular.noop, _error)
+      promise.then(_reset, _error)
 
 
 class Editor