Fix bogus assumption for live registers at safe point.

Fix bogus assumption for live registers at safe point.

We did not take into account inactive intervals going
into active when computing live registers at a slow path
safe point. So we must ensure the safepoint interval is always
handled after all intervals starting at the same position have
been handled.

Change-Id: I05ea2161016a90b0ee3ba0b18cd54a8e46860f1e