Auto-flush SiteIndexer's PrintWriters
Auto-flush SiteIndexer's PrintWriters

As the PrintWriters' auto-flush was not turned on, the last few
messages of a NoteDB migration still stuck in buffers when the
program stopped and they never made it to the screen.

To avoid swallowing (or delaying) output, we turn on auto-flushing.

Change-Id: Ib9f74c645a16ebe40717acff9e98c1275bc52518

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