Skip TestIndexPageMappings and test_url_image
Skip TestIndexPageMappings and test_url_image

These tests occasionally fail causing multiple failures on Travis and
Appveyor jobs. We can also mark them as expectedFailure, but that
would make noise on unexpected success messages during the tests, making
detection of unexpected success messages that can actually be fixed harder.

Bug: T193637
Bug: T181913
Change-Id: If1765d94cc798f37b228730e5d5adec302f7824c

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