Bug 1595666

Description of problem:
With etcd 3.2.22 or higher, the administrator can set a custom cipher-suite list with '--cipher-suites "comma-separated-cipher-list"'

It would be great to bring this to the OCP installer.

Steps to Reproduce:
1. Environment with etcd 3.2.22 or higher

2. Create a new env variable in /etc/etcd/etcd.conf, with a comma-separated cipher list:

~~~
ETCD_CIPHER_SUITES="TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305,TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256"
~~~

* changes should be in https://github.com/openshift/openshift-ansible/blob/master/roles/etcd/templates/etcd.conf.j2

3. Edit the ExecStart in the systemd unit to use this cipher list:

~~~
ExecStart=/bin/bash -c "GOMAXPROCS=$(nproc) /usr/bin/etcd --name=\"${ETCD_NAME}\" --data-dir=\"${ETCD_DATA_DIR}\" --cipher-suites \"${ETCD_CIPHER_SUITES}\" --listen-client-urls=\"${ETCD_LISTEN_CLIENT_URLS}\""
~~~

* I think the playbook should create a new systemd unit in /etc/systemd/... to avoid the default unit file to be overriden by the rpm (which by default overrides /usr/lib/systemd/...)

Expected results:
As an administrator I want to set my etcd cipher-suite list in my ansible host file.