GUACAMOLE-527: Add basic check for known hosts file for SSH connections.
GUACAMOLE-527: Add basic check for known hosts file for SSH connections.

glyptodon/guacamole-server,mike-jumper/incubator-guacamole-server,apache/guacamole-server,mike-jumper/incubator-guacamole-server,apache/guacamole-server,apache/guacamole-server,glyptodon/guacamole-server,glyptodon/guacamole-server,mike-jumper/incubator-guacamole-server,mike-jumper/incubator-guacamole-server