[1.7.x] Fixed #11775 -- Made ABSOLUTE_URL_OVERRIDES work with models that...

[1.7.x] Fixed #11775 -- Made ABSOLUTE_URL_OVERRIDES work with models that don't define get_absolute_url().

Thanks jukvalim for the report and initial patch,
and Preston Timmons for review.

Backport of c32bc1a7 from master