elf: _dl_find_object may return 1 during early startup (bug 30515)

Success is reported with a 0 return value, and failure is -1.
Enhance the kitchen sink test elf/tst-audit28 to cover
_dl_find_object as well.

Fixes commit 5d28a896 ("elf: Add _dl_find_object function")
and bug 30515.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>