Revert "Use real locations when opening dex files from the context"

This reverts commit 821a2595.

Reason for revert: Oat file assistant logic was updated to not
use realpaths anymore. So this is no longer needed.

Test: m test-art-host-gtest

Change-Id: Ia63a50f60b82ec3e20606d0be852607c9d2eb26e