Fix psutil DeprecationWarning
Since v6.0.0, psutil.Process.connections
is deprecated.
The replacement is psutil.Process.net_connections
. We use it if available,
but fallback to the old method if not. That way we don't need
to restrict the version of psutil installed with PyTango.
The deprecation warning causes tests to fail since we have configured pytest to convert warnings to errors.