Generate correct Exif data from capture metadata

The GPS metadata are supposed to by piped from request to result and
included in the jpeg Exif.

Additionnaly, flash, make and model are added in the exif metadata with
some default value since they are required.

Test: atest 'android.hardware.camera2.cts.StillCaptureTest#testJpegExif[1]'
Fixes: 324383963
Change-Id: Iaf161a2d9816115a0daba19dc2d9a911bc879330