Add missing card mark verification to CC

Easier than adapting the code in heap.cc to do this. The verification
ensures that objects on clean cards never reference objects in newly
allocated regions.

Revert some changes from aog/341344 that caused the verification to
fail.

Bug: 12687968

Test: test-art-host with CC

Change-Id: Iad583644bb76633ccea0dba87cb383f30adaa80b