Move container_of up (with related code, lru_run).

In previous reorganization of lru_run, the early return was moved
up, but assignment of entry was not moved, leading to an illegal
access.

Found (sort of) by Coverity, reported by Thomas Favre-Bulle
<thomas.favre-bulle@bull.net>.

Signed-off-by: Matt Benjamin <matt@linuxbox.com>