style

tests/phpunit/includes/StringUtilsTest.php:42:3
 - avoid function calls in a FOR loop test part

tests/phpunit/includes/PathRouterTest.php:155 to 165
 - fix space/tabs indenting
 - convert double quotes to single for consistency

tests/phpunit/data/xmp/7.result.php
 - reindent to use tabs instead of spaces
 - removed trailing whitespaces

tests/phpunit/includes/filebackend/FileBackendTest.php
 - spaces in indentation

Change-Id: I9c15803f961fc88b798ada3dd6c2b292c1de2143