fix r3695: this commit *) freed valid keys zone node *) and did not decrease cache size, so cache manager process ete CPU time,    if cache checking max_size was enabled
fix r3695: this commit
*) freed valid keys zone node
*) and did not decrease cache size, so cache manager process ete CPU time,
   if cache checking max_size was enabled

firebase/nginx,firebase/nginx,hy0kl/nginx,hy0kl/nginx,firebase/nginx,hy0kl/nginx,firebase/nginx