namespacing redis_analytics

redis analytics does not support Proc namespaces in its redis
connection.

Thus, we need to follow the same procedure as for sidekiq:
cef3620acf154df224746a1563
8ff2b0a4d05d11

Discussion: resque/redis-namespace#75

See also this stackoverflow question:
http://stackoverflow.com/q/40638628/2066546

Please note, this is just an intermediate step. Eventually, we will
move to separate redis server instances.

Internal trello cards:
https://trello.com/c/6xYBRb09/1075-redis-bottleneck
https://trello.com/c/cypH3vmW/896-multitenancy

(cherry picked from commit 9396e36)

config/initializers/redis_analytics.rb

@@ -3,8 +3,7 @@
 require_relative '../../app/models/redis_analytics/metrics'
 
 RedisAnalytics.configure do |configuration|
-  configuration.redis_connection = Redis.new(host: ENV['REDIS_HOST'], port: '6379')
-  configuration.redis_namespace = "#{::STAGE}_redis_analytics"
+  configuration.redis_connection = RedisConnectionConfiguration.new(:redis_analytics).to_namespaced_redis
 
   # We only want to track signed in users, not bots et cetera.
   #