Support using paramiko to set up accelerate connection

Adds original_transport attribute to Runner to track what the original
transport was before it is changed to 'accelerate'.
If using paramiko in original_transport, uses ParamikoConnection.  If
not, falls back to SSHConnection like before.

lib/ansible/runner/__init__.py

@@ -185,6 +185,7 @@ class Runner(object):
         self.accelerate       = accelerate
         self.accelerate_port  = accelerate_port
         self.callbacks.runner = self
+        self.original_transport = self.transport
 
         if self.accelerate:
             # if we're using accelerated mode, force the local