retain_task shouldn't kill appium in between session about appium

[vdelendik]

fixed. during the testing

1. run regular mobile sample test
   -> all 3 should executed, for each session video and session.log registered in the reporting
2. override capabilities.app to use invalid non existing path and execute test
   -> all 3 tests should fail but we should see for each of them session.log attached obligatory. for some of them even video might be generated
3. run with invalid path and device with pin
   -> all 3 tests should have session.log obligatory and 90% that video as well how device is unpined

Note: step 2 and 3 should be done only with 7.3.15+ or 7.3.15-SNAPSHOT as only in this version we deliver fallbackSessionId for reference. Exact reporting build and env - still TBD

[dhreben]

Verified.