Comment 4 for bug 1447084

Correct some words for above.

For kilo rc, we can fix it by pass an elevated context down to the db code, then we can keep the hypervisor api behavior as before.

For master code, it already fixed by https://review.openstack.org/#/c/160089/, but we can't backport it to kilo rc, this touch some base code. So it is too risk for kilo rc.