Add support for Google Cloud Memorystore

This adds an optional `redis_enable_client` config option that will turn
off the CLIENT command when talking to the Sidekiq API.

Relates to https://gitlab.com/gitlab-org/omnibus-gitlab/issues/4164
2 jobs for sh-support-google-cloud-memorystore in 35 seconds
Status Job ID Name Coverage
  Test
passed #4079272
rspec

00:00:34

passed #4079273
rubocop

00:00:34