Fix error due to use of private paramiko class attribute
Fix error due to use of private paramiko class attribute

This code relies on the internal mapping class in Paramiko, but the variable might hold a normal Python dictionary due to the previous lines, so it crashes when `self._host_keys.lookup(host_port)` is true. The keys to this virtual dictionary are already "x.key.get_name()", so it can be simplified to iterating over it.
earies/ncclient,nwautomator/ncclient,ncclient/ncclient