When running a config that specifies a SSH communicator with a bastion
without any authentication option, the proposed resolution would only
include password or private key, and left agent authentication out of
the error message.

This commit adds it to the list of options to resolve it.

When a SSH bastion is used for connecting to a target, the operation is
done completely silently, making it hard to understand if it is working
as intended.

To make it easier to follow the path that the command is taking, we add
a few more INFO/DEBUG logs that parrot the actions it takes for
connecting.