Fix roots filtering for move operations.

Add test coverage for the Downloads case.
This was a regression to my recent cleanup of RootInfo.
Fixed logic to not exclude basically *everything* when a
    directory is in the set of files to be copied.

Bug: 27303346
Change-Id: I4d5608e0d8d95448b027b20107a11a7a5e46d45e
2 files changed