Add retry to ensure service is reachable

Also modify Gemfile for ruby version issue

test/integration/standard/serverspec/spec_helper.rb

@@ -1,2 +1,11 @@
 require 'serverspec'
 set :backend, :exec
+
+require 'rspec/retry'
+
+RSpec.configure do |config|
+  # show retry status in spec process
+  config.verbose_retry = true
+  # show exception that triggers a retry if verbose_retry is set to true
+  config.display_try_failure_messages = true
+end