Aperture: Fix front camera intent preview mirroring

With image capture intents, properly mirror the preview image for a
front-facing camera photo when the "Mirror front camera" feature is on,
as is the default. Otherwise, in addition to not being mirrored like
the live preview, the image preview may appear to be upside down.

Issue: calyxos#2642
Change-Id: I49b6256750ac821c6eefdd28ed7a4c2ec1c519c9