Log ssh & scp related issues also on screen

Log ssh & scp related issues also on screen

When scripts are doing an ssh or scp to the PROX instances, errors were
sometimes hidden. E.g. when we try to upload a config file to the PROX
instance that is already existing but owned by another user, we would
not see the error on the screen.
Note this will only happen if you build your own image. In case you use
the pre-canned PROX images, this should not cause issues.

Change-Id: I94176b737cd548c93afc71450a85910d7eca2b0c
Signed-off-by: Luc Provoost <luc.provoost@intel.com>