Description of problem:
When run ansible playbooks directly, installer will prompt "Are you sure you want to continue connecting (yes/no)?". It's not convenient with many nodes.

Version-Release number of selected component (if applicable):
openshift3/installer:v3.2.0.15

How reproducible:
100%

Steps to Reproduce:
1. config the right key to ssh remote instance without password

2.docker run -ti -v ~/openshift/:/var/lib/openshift-installer/:Z -v ~/.ssh:/root/.ssh:Z openshift3/installer install

3.docker run --entrypoint=/usr/bin/ansible-playbook -ti -v ~/openshift/:/var/lib/openshift-installer/:Z -v ~/.ssh:/root/.ssh:Z openshift3/installer -i hosts /usr/share/ansible/openshift-ansible/playbooks/byo/config.yml

Actual results:
For step 3: quick-installer works well.     

For step 4:
4.GATHERING FACTS *************************************************************** 
<x.x.172.119> ESTABLISH CONNECTION FOR USER: root on PORT 22 TO x.x.172.119

paramiko: The authenticity of host 'x.x.172.119' can't be established.
The ssh-rsa key fingerprint is 1ea36996f185856f06a89b1e9e16e2eb.
Are you sure you want to continue connecting (yes/no)?
yes


Expected results:
Running well without asking "Are you sure you want to continue connecting (yes/no)"

Additional info: