Camera2 Legacy: Set a default thumbnail size

Generally, JPEGs are better with thumbnails, and the default parameters
typically set a basic thumbnail size. In legacy, include a default size in the
templates.

This also works around issues with some devices not producing valid images with no
thumbnail.

Bug: 17724701
Change-Id: I2ad1449fc8c6d1fdec609af55f53db7491abbb92