Fix RestAssured URL handling and unexpected restarts in QuarkusProdModeTest

This is fixing an issue we had over at https://github.com/quarkiverse/quarkus-cxf/pull/669#issuecomment-1382911655 (cc @shumonsharif @ppalaga).

Without this fix QuarkusProdModeTest does the following when `run` and `expectExit` are enabled:

• `beforeAll`:
• start the app and wait for it to exit
• setup RestAssured URL (`RestAssuredURLManager` stores the previous port)
• `beforeEach` :
• again start the app and wait for it to exit
• again setup RestAssured URL, loosing the initially stored port to restore
• `afterAll`:
• clear the RestAssured URL, but not with the initially stored port

This fix:

• makes sure that the app is not stared again for each test method when `expectExit` is enabled
• does not even set up RestAssured URL when `expectExit` is enabled (App will have exited anyway)
• make setup/clean of RestAssured URL consistent with (manual) `start()`/`stop()`

Please note that there can still be inconsistencies w.r.t. to the URL when using multiple `QuarkusProdModeTest`s because there is only one static URL Manager, not one for each extension.