Fix method setup in authorization-scopes.test

Fix the code builing a scoped method to correctly handle the case
when the setup method is called twice and the previously defined
method has to be overriden with new remoting metadata.

test/authorization-scopes.test.js

@@ -82,6 +82,10 @@ describe('Authorization scopes', () => {
   }
 
   function givenRemoteMethodWithCustomScope() {
+    // Delete any previosly registered instance of the method "scoped"
+    User.sharedClass._methods = User.sharedClass._methods
+      .filter(m => m.name !== 'scoped');
+
     const accessScopes = arguments[0] || [CUSTOM_SCOPE];
     User.scoped = function(cb) { cb(); };
     User.remoteMethod('scoped', {