Fix `keys` metric being zero
Fix `keys` metric being zero

brajput24/redis-stat,cheftestn/redis-stat,jerrysearch/redis-stat,taohaolong/redis-stat,taohaolong/redis-stat,junegunn/redis-stat,brajput24/redis-stat,cheftestn/redis-stat,jerrysearch/redis-stat,junegunn/redis-stat,jerrysearch/redis-stat,taohaolong/redis-stat,brajput24/redis-stat,junegunn/redis-stat,cheftestn/redis-stat