Split testImageusage into four tests
Split testImageusage into four tests

There is a reoccurring problem with this test method on English Wikipedia.
As the test currently has four different sets of tests, it is not 100%
reliable to determine which queries are causing the problem.

Output message regarding which image is being used in these tests.

Bug: 71971
Change-Id: I8443bc0f55ff77b8fc266f55c2bfbf32940be892

icyflame/batman,npdoty/pywikibot,TridevGuha/pywikibot-core,wikimedia/pywikibot-core,wikimedia/pywikibot-core,emijrp/pywikibot-core,jayvdb/pywikibot-core,happy5214/pywikibot-core,h4ck3rm1k3/pywikibot-core,PersianWikipedia/pywikibot-core,hasteur/g13bot_tools_new,h4ck3rm1k3/pywikibot-core,Darkdadaah/pywikibot-core,magul/pywikibot-core,trishnaguha/pywikibot-core,magul/pywikibot-core,Darkdadaah/pywikibot-core,hasteur/g13bot_tools_new,npdoty/pywikibot,smalyshev/pywikibot-core,xZise/pywikibot-core,hasteur/g13bot_tools_new,darthbhyrava/pywikibot-local,happy5214/pywikibot-core,VcamX/pywikibot-core,valhallasw/pywikibot-core,jayvdb/pywikibot-core