Force scans when publishing.

If a clever app had already written the exact size and modified time
of a file before publishing, we'd skip scanning that item.  To force
a scan, clear these columns when publishing to force a scan.

Bug: 134590552
Test: atest --test-mapping packages/providers/MediaProvider
Change-Id: Ibec29976fa2821e77f3b799c9e3a9be08e34bf6c
1 file changed