fix PathProbe

We must push the probe's scope last, because otherwise the file scope
would shadow property names like fileName and filePath.

Task-number: QBS-383
Change-Id: I4c78b6ad65c2f3e9af5c5c4dda721f6bb6475324
Reviewed-by: Christian Kandeler <christian.kandeler@digia.com>
use PathProbe in dynamicRuleOutputs test

That's more generic and adds a Probe usage to the test suite.

Change-Id: I022022f9c1d77d5508fbbe848ce56a73eb115185
Reviewed-by: Jake Petroules <jake.petroules@petroules.com>
Reviewed-by: Christian Kandeler <christian.kandeler@digia.com>