Only save Peek session in Redis when Peek is enabled

Signed-off-by: Rémy Coutable <remy@rymai.me>

config/initializers/peek.rb

@@ -42,3 +42,6 @@ class PEEK_DB_CLIENT
 end
 PEEK_DB_VIEW.prepend ::Gitlab::PerformanceBar::PeekQueryTracker
+
+require 'peek/adapters/redis'
+Peek::Adapters::Redis.prepend ::Gitlab::PerformanceBar::RedisAdapterWhenPeekEnabled

lib/gitlab/performance_bar/redis_adapter_when_peek_enabled.rb

+# frozen_string_literal: true
+
+# Adapted from https://github.com/peek/peek/blob/master/lib/peek/adapters/redis.rb
+module Gitlab
+  module PerformanceBar
+    module RedisAdapterWhenPeekEnabled
+      def save
+        super unless ::Peek.request_id.blank?
+      end
+    end
+  end
+end