Set redis file descriptor limit when run via pacemaker

Set redis file descriptor limit when run via pacemaker

The current redis file descriptor limit is 4096 because of two reasons:
- It is run via the redis user
- It is not started via systemd which has explicit LimitNOFILE set to
  10240 (which matches the default configuration of maximum 10000
  clients)

Create an /etc/security/limits.d/redis.conf file in order to increase
the fd limit value  With this change we correctly get the following
limits:
[root@overcloud-controller-0 ~]# pcs status |grep -A2 redis
 Master/Slave Set: redis-master [redis]
     Masters: [ overcloud-controller-2 ]
     Slaves: [ overcloud-controller-0 overcloud-controller-1 ]

[root@overcloud-controller-0 ~]# cat /proc/`pgrep redis`/limits | grep open
Max open files            10240                10240   files

Previously this limit was set to 4096.

Change-Id: I7691581bad92ad9442cecd82cf44f5ac78ed169f
Closes-Bug: #1635334