ExifInterface: Update Pixel X/Y Dimension tag values

Current code checks Pixel X/Y Dimension tags when updating primary
image size values. This creates a problem when the image data are not
placed properly (IFD_TYPE_PRIMARY may need to be swapped with
IFD_TYPE_PREVIEW). This CL moves the updating code to after the
images have been properly placed.

Bug: 29409358
Change-Id: Ia70b5b292812c1e7812e9fc8ca2434998cf1b7f9