Remove limits for redis in /etc/security/limits.d

Remove limits for redis in /etc/security/limits.d

Now that puppet-redis supports ulimit for cluster managed redis (via
https://github.com/arioch/puppet-redis/pull/192), we need to remove the
file snippet as otherwise we will get a duplicate resource error.

We will need to create a THT change that at the very least sets the
redis::managed_by_cluster_manager key to true so that
/etc/security/limits.d/redis.conf gets created.
We also add code to not break backwards compatibility with the old hiera
key.

Change-Id: I4ffccfe3e3ba862d445476c14c8f2cb267fa108d
Partial-Bug: #1688464