Fix locking order reversal in arena_reset().
Fix locking order reversal in arena_reset().

8l/jemalloc,glandium/jemalloc,wqfish/jemalloc,wqfish/jemalloc,glandium/jemalloc,8l/jemalloc,wqfish/jemalloc,wqfish/jemalloc,glandium/jemalloc,wqfish/jemalloc,glandium/jemalloc,8l/jemalloc,8l/jemalloc