Adds another test to btrfs_test.
Adds another test to btrfs_test.

wideioltd/pachyderm,alexdebrie/pachyderm,phacops/pachyderm,pachyderm/pfs,ShengjieLuo/pachyderm,pachyderm/pfs,ShengjieLuo/pachyderm,phacops/pachyderm,kunthar/pachyderm,klucar/pachyderm,sambooo/pachyderm,kunthar/pachyderm,alexdebrie/pachyderm,henrylee2cn/pachyderm,sambooo/pachyderm,wideioltd/pachyderm,klucar/pachyderm,klucar/pachyderm,pachyderm/pfs,ShengjieLuo/pachyderm,alexdebrie/pachyderm,henrylee2cn/pachyderm,sambooo/pachyderm