Use Gitlab::CurrentSettings in UrlValidator

Gitlab::CurrentSettings will create ApplicationSetting.current if not
present which means we don't have to use `&.`. We can also more easily
use stub_application_setting in specs

app/validators/url_validator.rb

@@ -93,6 +93,6 @@ class UrlValidator < ActiveModel::EachValidator
   end
 
   def allow_setting_local_requests?
-    ApplicationSetting.current&.allow_local_requests_from_hooks_and_services?
+    Gitlab::CurrentSettings.allow_local_requests_from_hooks_and_services?
   end
 end

spec/lib/gitlab/current_settings_spec.rb

@@ -14,9 +14,8 @@ describe Gitlab::CurrentSettings do
 
   describe '#current_application_settings', :use_clean_rails_memory_store_caching do
     it 'allows keys to be called directly' do
-      db_settings = create(:application_setting,
-        home_page_url: 'http://mydomain.com',
-        signup_enabled: false)
+      db_settings = ApplicationSetting.first || create(:application_setting)
+      db_settings.update!(home_page_url: 'http://mydomain.com', signup_enabled: false)
 
       expect(described_class.home_page_url).to eq(db_settings.home_page_url)
       expect(described_class.signup_enabled?).to be_falsey
@@ -109,7 +108,7 @@ describe Gitlab::CurrentSettings do
 
         context 'with pending migrations' do
           before do
-            expect(ActiveRecord::Migrator).to receive(:needs_migration?).and_return(true)
+            allow(ActiveRecord::Migrator).to receive(:needs_migration?).and_return(true)
           end
 
           shared_examples 'a non-persisted ApplicationSetting object' do

spec/models/lfs_download_object_spec.rb

@@ -46,9 +46,7 @@ describe LfsDownloadObject do
         subject { described_class.new(oid: oid, size: size, link: 'http://192.168.1.1') }
 
         before do
-          allow(ApplicationSetting)
-            .to receive(:current)
-              .and_return(ApplicationSetting.build_from_defaults(allow_local_requests_from_hooks_and_services: setting))
+          stub_application_setting(allow_local_requests_from_hooks_and_services: setting)
         end
 
         context 'are allowed' do