Add the rails runner command as a known runtime

Otherwise users get runtime identification errors when
omnibus-gitlab adds instance level apps for auth, like
grafana and mattermost.

lib/gitlab/runtime.rb

@@ -12,6 +12,7 @@ module Gitlab
       :console,
       :geo_log_cursor,
       :puma,
+      :rails_runner,
       :rake,
       :sidekiq,
       :test_suite,
@@ -64,6 +65,10 @@ module Gitlab
         !!defined?(::GeoLogCursorOptionParser)
       end
 
+      def rails_runner?
+        !!defined?(::Rails::Command::RunnerCommand)
+      end
+
       def web_server?
         puma? || unicorn?
       end

spec/lib/gitlab/runtime_spec.rb

@@ -97,4 +97,12 @@ describe Gitlab::Runtime do
 
     it_behaves_like "valid runtime", :geo_log_cursor, 1
   end
+
+  context "rails runner" do
+    before do
+      stub_const('::Rails::Command::RunnerCommand', double('::Rails::Command::RunnerCommand'))
+    end
+
+    it_behaves_like "valid runtime", :rails_runner, 1
+  end
 end