give each tree cache its unique channel to avoid multiple close on the same channel
give each tree cache its unique channel to avoid multiple close on the same channel

Signed-off-by: Ye Ji <f94739373a5e2c903a507c075effad238d7b7494@hioscar.com>

kangwoo/prometheus,alileza/prometheus,GoogleCloudPlatform/prometheus,GoogleCloudPlatform/prometheus,Gouthamve/prometheus,alileza/prometheus,keegancsmith/prometheus,prometheus/prometheus,Gouthamve/prometheus,keegancsmith/prometheus,Gouthamve/prometheus,keegancsmith/prometheus,kangwoo/prometheus,alileza/prometheus,alileza/prometheus,prometheus/prometheus,prometheus/prometheus,kangwoo/prometheus,kangwoo/prometheus,prometheus/prometheus,prometheus/prometheus,Gouthamve/prometheus,keegancsmith/prometheus,GoogleCloudPlatform/prometheus,alileza/prometheus,keegancsmith/prometheus,GoogleCloudPlatform/prometheus,GoogleCloudPlatform/prometheus