Fix entry->attr_lock order violation (exports).

Code entring the LRU system with an entry cannot in general
do so while holding the entry attr_lock.  Doing so violates the
lock ordering.

Coverity CID 62085.

Signed-off-by: Matt Benjamin <matt@linuxbox.com>
Acked-by: Frank S. Filz <ffilzlnx@mindspring.com>