Merge branch 'quarantine-flaky-specs' into 'master'

Put four flaky specs in quanrantine

See merge request gitlab-org/gitlab-ce!27456

spec/features/projects/files/user_edits_files_spec.rb

@@ -171,7 +171,7 @@ describe 'Projects > Files > User edits files', :js do
         wait_for_requests
       end
-      it 'links to the forked project for editing' do
+      it 'links to the forked project for editing', :quarantine do
         click_link('.gitignore')
         find('.js-edit-blob').click

spec/features/projects/wiki/user_creates_wiki_page_spec.rb

@@ -141,7 +141,7 @@ describe "User creates wiki page" do
         end
       end
-      it_behaves_like 'wiki file attachments'
+      it_behaves_like 'wiki file attachments', :quarantine
     end
     context "in a group namespace", :js do
@@ -151,7 +151,7 @@ describe "User creates wiki page" do
         expect(page).to have_field("wiki[message]", with: "Create home")
       end
-      it "creates a page from the home page" do
+      it "creates a page from the home page", :quarantine do
         page.within(".wiki-form") do
           fill_in(:wiki_content, with: "My awesome wiki!")

spec/lib/gitlab/background_migration/migrate_build_stage_spec.rb

@@ -51,7 +51,7 @@ describe Gitlab::BackgroundMigration::MigrateBuildStage, :migration, schema: 201
                                                       statuses[:pending]]
   end
-  it 'recovers from unique constraint violation only twice' do
+  it 'recovers from unique constraint violation only twice', :quarantine do
     allow(described_class::Migratable::Stage)
       .to receive(:find_by).and_return(nil)