refs #3227 integration tests: check file length before trying to check if the string is equal for non xml output; that prevents some outofmemory exceptions for longer files
mark test as incomplete if an expected output file is missing

git-svn-id: http://dev.piwik.org/svn/trunk@6897 59fd770c-687e-43c8-a1e3-f5a4ff64c105