Fix openAssetFile method of inserting photos.

For reference, the issue was occurring because the file descriptor
passed back to the caller is parceled immediately, which closes the
file descriptor on the provider side before it even gets to the
caller.  The solution was to stop fiddling around with temp files
and just pass back a pipe instead - the provider then can simply
read the image content from the pipe and process it.

Bug 5156644

Change-Id: Ie210f65b5b8681524fed12a53df0c852fc951e5a
3 files changed