Prevent SSH client proxy loops

Avoid creating a SSH client with a proxy client having the same
connection parameters. This will prevent from creating a SSH tunnel
within the same client.

This patch also provides aditional information in the exception
message, in case of SSH connection error, about the proxy client
configured in the SSH client.

Change-Id: I4fcffb7e26b0adc0e39dc13085f93db6495c3bd6
Related-Bug: #1860586
2 files changed