Fallback to byte-by-byte copy/move if optimized fails.

Sometimes providers may refuse to do a provider-side copy/move
even though the documents had the SUPPORTS_COPY/MOVE flags set.

This is because optimized copy/move may be only supported within
the same root.

Since there is no easy way to check if documents are on the same
roots from DocumentsUI, as well as whether the provider can actually
copy/move efficiently between different roots, we should tolerate the
failure and do a fallback to byte-by-byte operation.

Bug: 27436368
Change-Id: Ia1a0fbdba26c06b2151afc25d8513c01d60d31db