[bugfix] Start each test with empty page cache
[bugfix] Start each test with empty page cache

Bug: T175486
Change-Id: I3b6db2eb6a1980b0a720743269506df4a05d86a2

magul/pywikibot-core,PersianWikipedia/pywikibot-core,wikimedia/pywikibot-core,wikimedia/pywikibot-core,magul/pywikibot-core