Avoid using remote/local as (not user visible) names. 'internal'
means 'whatever the current target does', i.e. could be a remote setup,
'external' means 'attach to something running or waiting.

Also user setServerUrl() directly on the worker, no need go through
the 'opaque connection' mechanism here.

Change-Id: Id0e694562ce7d3129c7d0b790c91d465de24b4e4
Reviewed-by: Christian Stenger <christian.stenger@qt.io>