fix ssh_config inventory plugin to work with paramiko 1.7.2 till 1.15.1

The parsed dict from ssh_config is different across various versions on Paramiko. I made it to work with versoins from 1.7.2 to 1.15.1 (current newest in pip). Ubuntu 12.04 has now 1.7.7 and CentOS 6.5. has 1.7.5, so I think that's compatible enough.