QAART 412: Fixing the ImageStorage test

The main change is to use dedicated test files instead of random image file from the Special:NewFile page. The problems with using random file is that if a file with long revision history is chosen, the test would file.

https://wikia-inc.atlassian.net/browse/QAART-412
@ludwikkazmierczak, there is still notification. The problem with notification is that it goes away completely after 2-3 seconds, which is causing the test to have a pass rate at about 60-70%. By removing the check for this visual flash image, the test is still verifying that "Rename" still functions properly.