ExifInterface: Correct thumbnail compression info

Exifinterface sets the thumbnail's compression information as JPEG
whenever the image has no compression tag in it. As a result, even
an image with no thumbnail can have the thumbnail compression info.
This CL fixes the problem.

Test: Run CTS test on angler
Change-Id: I4b06956b1bac672e1bf235df6f458b31e8ee82bb