DngCreator: Don't use default locale for writing date/time into DNG

Explictly use Locale.US since EXIF/TIFF date/time fields require it.

Test: Switch to Arabic locale, verify no crash and resulting DNGs have valid metadata,
    plus CTS DngCreatorTest passes.
Bug: 65748590

Change-Id: I729ee6d849f7a39e5d396cfd8dd5d44325381822
1 file changed