packaging: setup: remote_engine: support older paramiko

Support el6's version of paramiko in which SFTPFile is not a context
manager.

Change-Id: I730d15670bd9aa5dc68d6d1f93157c5895429491
Bug-Url: https://bugzilla.redhat.com/1150498
Signed-off-by: Yedidyah Bar David <didi@redhat.com>