Description of problem:
Fail to upgrade ocp v3.7 to latest v3.9 when backup etcd due to wrong etcdctl command was set.

TASK [etcd : Generate etcd backup] *********************************************
task path: /usr/share/ansible/openshift-ansible/roles/etcd/tasks/backup/backup.yml:52
fatal: [x.x.x.x]: FAILED! => {"changed": false, "cmd": "runc exec etcd etcdctl backup --data-dir=/var/lib/etcd/ --backup-dir=/var/lib/etcd//openshift-backup-pre-upgrade-20180412085041", "msg": "[Errno 2] No such file or directory", "rc": 2}

#roles/etcd/defaults/main.yaml
r_etcd_common_etcdctl_command: "{{ 'etcdctl' if r_etcd_common_etcd_runtime == 'host' | bool else 'docker exec etcd_container etcdctl' if r_etcd_common_etcd_runtime == 'docker' else 'runc exec etcd etcdctl' }}"


Version-Release number of the following components:
openshift-ansible-3.9.20-1.git.0.f99fb43.el7.noarch

How reproducible:
always

Steps to Reproduce:
1. RPM install ocp v3.7
2. Run upgrade to v3.9
3.

Actual results:
Upgrade failed.

Expected results:
Upgrade succeed.

Additional info:
Please attach logs from ansible-playbook with the -vvv flag