Simplify SD update throttling (#4523)
Simplify SD update throttling (#4523)

* simplfied SD updates throtling

Signed-off-by: Krasi Georgiev <92e9bca555ae3f6bf713b708c97f3f6dcff65542@redhat.com>

* add default to catch cases when we don't have new updates.

Signed-off-by: Krasi Georgiev <92e9bca555ae3f6bf713b708c97f3f6dcff65542@redhat.com>

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