Allow users to edit photos for read-only contacts again

Similar to ag/711429 (for editing read-only names), we set the
photo bitmap from the read-only contact but set the newly created
(and writable) raw contact as the delta underlying the photo editor
view so that if the photo is updated by the user, the new raw
contact is set as changed and not the read-only raw contact.

Bug 21873945

Change-Id: Ibd40f3d708332fe6f87d247773b871d575d7d12e