Rewrite or remove Cisco Transport to decouple from SSH Transport

[clintoncwolfe]

Description

The Cisco IOS transport was implemented in such a way that it is tightly coupled to the SSH transport. As their level of "coreness" and support are very different, we want to be able to distribute and iterate on them separately.

Train and Platform Version

1.7.x and 2.x at least.

Replication Case

In the transports/ssh.rb, it includes the Cisco transport

Possible Solutions

Create a train-cisco transport plugin, and have it have-a SSH connection that it uses. See train-habitat for prior art.