CBQE-0 increase paramiko session timeout
from 10 mins to 15 mins

Change-Id: I67f66d2193aae5040b04c17aab912919cb8e5ffe
Reviewed-on: http://review.couchbase.org/43209
Reviewed-by: Thuan Nguyen <soccon@gmail.com>
Tested-by: Thuan Nguyen <soccon@gmail.com>