Allow to delete answers if the poll has not started yet

Deleting answers was not even possible. But it was possible to delete
questions. So we implemented the same behavior.

spec/system/admin/poll/questions/answers/answers_spec.rb

@@ -71,6 +71,21 @@ describe "Answers", :admin do
     expect("Another title").to appear_before("New title")
   end
 
+  scenario "Destroy" do
+    answer = create(:poll_question_answer, poll: future_poll, title: "I'm not useful")
+
+    visit admin_question_path(answer.question)
+
+    within("tr", text: "I'm not useful") do
+      accept_confirm("Are you sure? This action will delete \"I'm not useful\" and can't be undone.") do
+        click_button "Delete"
+      end
+    end
+
+    expect(page).to have_content "Answer deleted successfully"
+    expect(page).not_to have_content "I'm not useful"
+  end
+
   scenario "Reorder" do
     question = create(:poll_question)
     create(:poll_question_answer, question: question, title: "First", given_order: 1)