[webui] redirect to home after login from /user/do_login

If a user enters wrong credentials in login widget and he gets redirected to /user/do_login.
If login happens with correct credentials now the user is logged in but stays on the page and sees the login form again in master, or gets an 404 in 2.6.

Now he gets redirected into home if the user comes from the login page.

fixes #1557

src/api/app/controllers/webui/user_controller.rb

@@ -36,7 +36,11 @@ def do_login
 
     session[:login] = User.current.login
 
-    redirect_back_or_to root_path
+    if request.referer.end_with?("/user/login")
+      redirect_to home_path
+    else
+      redirect_back_or_to root_path
+    end
   end
 
   def show

src/api/test/functional/webui/user_controller_test.rb

@@ -181,6 +181,22 @@ def test_that_redirect_after_login_works # spec/controllers/webui/users_spec.rb
     assert_equal search_path, current_path
   end
 
+  def test_that_redirect_from_user_do_login_works # spec/controllers/webui/users_spec.rb
+    use_js
+
+    visit search_path
+    click_link("Log In")
+    fill_in 'Username', with: "tom"
+    fill_in 'Password', with: "brokenpassword"
+    click_button 'Log In'
+
+    fill_in 'Username', with: "tom"
+    fill_in 'Password', with: "buildservice"
+    click_button 'Log In'
+
+    assert_equal "tom", find('#home-username').text
+  end
+
   def test_redirect_after_register_user_action_works # spec/controllers/webui/users_spec.rb
     visit user_register_user_path
     within ".sign-up" do