[Autopilot-test] data needs to be clean

In some autopilot-tests from Jenkins-bot, the console output shows a wrong database version number:

qml: db version: 1.1 // the correct number is 1.2 since half year ago
file:///usr/share/shorts-app/databasemodule_v2.js:41: Error: duplicate column name: author Unable to execute statement

output can be found here:
http://91.189.93.70:8080/job/generic-mediumtests-vivid/466/testReport/junit/shorts_app.tests.test_rssreader/TestMainWindow/test_open_listmode_feed_item_with_mouse_/

So I suggest delete all data in ~/.local/share/com.ubuntu.shorts/