Setting keepalive option before opening session

Setting the keepalive option before opening up the paramiko session
in order to avoid the slim chance that the connection is stalled
in the short time between opening the session and setting up the
keepalive. I described the issue I am solving at
https://groups.google.com/forum/#!topic/ansible-project/rkwvz3vyvLk
Merge pull request #9462 from tkinz27/paramiko_keepalive

Setting keepalive option before opening session