toaster.bbclass: attach image file scan postfunc to do_image_complete
The postfunc for finding image files after completion of a build
fails, as the image files we're interested in don't exist at the
point when the scan is currently done (following do_rootfs).
Attach the postfunc for scanning for image files to the new
do_image_complete task, which definitely runs after the image files
have been created.
[YOCTO #8956]
Signed-off-by: Elliot Smith <elliot.smith@intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
