Use threads in open experiment/trace for long init operations

Use threads in open experiment/trace for long init operations

Additionally, the error handling in open experiment/trace
is changed to dispose the trace object in an error case. Also
some error print-outs are updated.

Change-Id: I49c9d8fbf04a83b2b7d3c36acbc52c1daa831998
Reviewed-on: https://git.eclipse.org/r/8836
Tested-by: Hudson CI
Reviewed-by: Alexandre Montplaisir <alexmonthy@voxpopuli.im>
IP-Clean: Alexandre Montplaisir <alexmonthy@voxpopuli.im>
Reviewed-by: Patrick Tasse <patrick.tasse@gmail.com>
IP-Clean: Patrick Tasse <patrick.tasse@gmail.com>