kettle: drop streamingBuffer check from monitor
kettle: drop streamingBuffer check from monitor

We're frequently crashing because `estimatedBytes` isn't reliably in
the `streamingBuffer` table property. We don't actually look at the data
from streamingBuffer anyway, so drop it.

cjwagner/test-infra,dims/test-infra,kubernetes/test-infra,jessfraz/test-infra,michelle192837/test-infra,BenTheElder/test-infra,michelle192837/test-infra,BenTheElder/test-infra,kubernetes/test-infra,kubernetes/test-infra,cjwagner/test-infra,michelle192837/test-infra,cjwagner/test-infra,kubernetes/test-infra,jessfraz/test-infra,michelle192837/test-infra,michelle192837/test-infra,jessfraz/test-infra,BenTheElder/test-infra,BenTheElder/test-infra,jessfraz/test-infra,dims/test-infra,cjwagner/test-infra,dims/test-infra,dims/test-infra,jessfraz/test-infra,kubernetes/test-infra,dims/test-infra,cjwagner/test-infra,michelle192837/test-infra,cjwagner/test-infra,dims/test-infra,BenTheElder/test-infra,BenTheElder/test-infra,kubernetes/test-infra,jessfraz/test-infra