Use proper URL generation function (#24576)

Fixes the redirection after login, otherwise `core/files/index` is opened which fails.

core/Controller/LoginController.php

 				return new RedirectResponse($location);
 			}
 		}
-		return new RedirectResponse($this->urlGenerator->linkTo('files', 'index'));
+		return new RedirectResponse($this->urlGenerator->linkToRoute('files.view.index'));
 	}
 
 }

tests/core/controller/LoginControllerTest.php

 			->method('createSessionToken')
 			->with($this->request, $user->getUID(), $password);
 		$this->urlGenerator->expects($this->once())
-			->method('linkTo')
-			->with('files', 'index')
+			->method('linkToRoute')
+			->with('files.view.index')
 			->will($this->returnValue($indexPageUrl));
 
 		$expected = new \OCP\AppFramework\Http\RedirectResponse($indexPageUrl);