Bug 1462087

Description of problem:
When running migration from previous containerized etcd to system container etcd, installer failed when trying to mask etcd_container service:

For containerized etcd installation, etcd container service file was created as /etc/systemd/system/etcd_container.service
https://github.com/openshift/openshift-ansible/blob/openshift-ansible-3.6.112-1/roles/etcd/tasks/main.yml#L21
In etcd system_container.yaml, it will try to mask the etcd_container service
https://github.com/openshift/openshift-ansible/blob/openshift-ansible-3.6.112-1/roles/etcd/tasks/system_container.yml#L39

[root@ip-172-18-4-95 ~]# systemctl status etcd_container
● etcd_container.service - The Etcd Server container
   Loaded: loaded (/etc/systemd/system/etcd_container.service; enabled; vendor preset: disabled)
   Active: active (running) since Thu 2017-06-15 23:24:10 EDT; 3h 12min ago
 Main PID: 14689 (docker-current)
   Memory: 5.9M
   CGroup: /system.slice/etcd_container.service
           └─14689 /usr/bin/docker-current run --name etcd_container --rm -v /var/lib/etcd/:/var/lib/etcd/:z -v /etc/etcd:/etc/etcd:ro --env-file=/etc/etcd/etcd.conf --ne...

[root@ip-172-18-4-95 ~]# ls -al /etc/systemd/system/etcd_container.service
-rw-r--r--. 1 root root 576 Jun 15 22:58 /etc/systemd/system/etcd_container.service

[root@ip-172-18-4-95 ~]# ls -al /usr/lib/systemd/system/etcd_container.service
ls: cannot access /usr/lib/systemd/system/etcd_container.service: No such file or directory

[root@ip-172-18-4-95 ~]# systemctl stop etcd_container

[root@ip-172-18-4-95 ~]# systemctl disable etcd_container
Removed symlink /etc/systemd/system/docker.service.wants/etcd_container.service.

[root@ip-172-18-4-95 ~]# systemctl mask etcd_container
Failed to execute operation: Invalid argument


Version-Release number of selected component (if applicable):
openshift-ansible-3.6.112-1.git.0.1ce58b5.el7.noarch

How reproducible:
Always

Steps to Reproduce:
1.Setup a containerized ocp-3.6 cluster, etcd docker container is running and etcd_container service is running.

2.Add use_etcd_system_container=true into ansible inventory file, run installation playbook again

Actual results:
TASK [etcd : Disable etcd_container] *******************************************
fatal: [ec2-52-206-163-36.compute-1.amazonaws.com]: FAILED! => {
    "changed": false, 
    "failed": true, 
    "failed_when_result": true
}

MSG:

Unable to mask service etcd_container: Failed to execute operation: Invalid argument


Expected results:


Additional info: