Merge branch 'downgrade-redis-3-2-2' into 'master'

Downgrade to Redis 3.2.2 due to massive memory leak with Sidekiq

This affects GitLab 8.8 and 8.9. See:

* https://github.com/mperham/sidekiq/blob/master/Changes.md#413
* https://gitlab.com/gitlab-org/gitlab-ce/issues/19441

See merge request !5056
(cherry picked from commit 4b0bd4f8)

CHANGELOG

 Please view this file on the master branch, on stable branches it's out of date.
 
 v 8.9.5
+  - Downgrade to Redis 3.2.2 due to massive memory leak with Sidekiq. !5056
   - Re-enable import button when import process fails due to namespace already being taken. !5053
   - Fix snippets comments not displayed. !5045
   - Fix emoji paths in relative root configurations. !5027

Gemfile.lock

@@ -566,7 +566,7 @@ GEM
     recaptcha (3.0.0)
       json
     redcarpet (3.3.3)
-    redis (3.3.0)
+    redis (3.2.2)
     redis-actionpack (4.0.1)
       actionpack (~> 4)
       redis-rack (~> 1.5.0)