Description of problem:
Upgrade against ocp with dedicated etcd hosts. Upgrade failed when check backup etcd in phase 3.7 to 3.8. It seems that Play [Backup etcd] was not run due to a missing module when gather facts.

TASK [Gather Cluster facts] ****************************************************
task path: /usr/share/ansible/openshift-ansible/playbooks/init/cluster_facts.yml:9
fatal: [x.x.x.x]: FAILED! => {"changed": false, "module_stderr": "Shared connection to x.x.x.x closed.\r\n", "module_stdout": "Traceback (most recent call last):\r\n  File \"/tmp/ansible_FSLoJO/ansible_module_openshift_facts.py\", line 18, in <module>\r\n    import ipaddress\r\nImportError: No module named ipaddress\r\n", "msg": "MODULE FAILURE", "rc": 0}

<--snip-->
PLAY [Backup etcd] *************************************************************

PLAY [Gate on etcd backup] *****************************************************

TASK [Gathering Facts] *********************************************************
ok: [localhost]
META: ran handlers

TASK [set_fact] ****************************************************************
task path: /usr/share/ansible/openshift-ansible/playbooks/openshift-etcd/private/upgrade_backup.yml:18
ok: [localhost] => {"ansible_facts": {"etcd_backup_completed": []}, "changed": false}

TASK [set_fact] ****************************************************************
task path: /usr/share/ansible/openshift-ansible/playbooks/openshift-etcd/private/upgrade_backup.yml:22
ok: [localhost] => {"ansible_facts": {"etcd_backup_failed": [x.x.x.x]}, "changed": false}

TASK [fail] ********************************************************************
task path: /usr/share/ansible/openshift-ansible/playbooks/openshift-etcd/private/upgrade_backup.yml:24
fatal: [localhost]: FAILED! => {"changed": false, "msg": "Upgrade cannot continue. The following hosts did not complete etcd backup: qe-jliu-rp1-etcd-1.0131-gy1.qe.rhcloud.com"}

Version-Release number of the following components:
ansible-2.4.2.0-2.el7.noarch
openshift-ansible-3.9.0-0.34.0.git.0.c7d9585.el7.noarch

How reproducible:
always

Steps to Reproduce:
1. Install ocp with dedicated etcd
2. Run upgrade against above ocp
ansible-playbook /usr/share/ansible/openshift-ansible/playbooks/byo/openshift-cluster/upgrades/v3_9/upgrade_control_plane.yml
3.

Actual results:
Upgrade failed

Expected results:
Upgrade succeed.

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