REST API: Restore Autosaves controller test for multisite.

PHPUnit 3.6.x requires `exclude` and `file` paths to be relative to the checkout root.

PHPUnit 4.0.0+ requires the paths to be relative to the configuration file.

Merges [43774] from the 5.0 branch to trunk.

See #45131.

Built from https://develop.svn.wordpress.org/trunk@44128


git-svn-id: https://core.svn.wordpress.org/trunk@43958 1a063a9b-81f0-0310-95a4-ce76da25c4cd