Allow user move/copy more than 500+ items.

This used to fail because UrisSupplier#getUris cannot be called more
than once when it's backed up by a JumboUrisSupplier. It's getting
called twice at the moment: once to acquire archives, and another time
by buildDocumentList(). This guarantees failure every time when copying
500+ files.

Test: Auto tests & manual test.
Bug: 37882979
Change-Id: I0ae2f829d709d753245818da16524d2755187d3c
(cherry picked from commit b1d56121)