"live calls" view counts 4xx responses as success

Nobody has claimed this yet.

## Bug Report

### What is the issue?

In the "live calls" view for a deployment, it appears that the success rate calculation appears to not count 404 errors against the success rate. This leads to the disconcerting effect of 10qps of 404 traffic being accounted as "100% successful"

### How can it be reproduced?

Send a large number of requests to a meshed service for a nonexistent path. :)

### Logs, error output, etc



(You'll have to take it on faith that the second screenshot there elides a very large number of 404s. :)

#### `linkerd check` output

```text
kubernetes-api
--------------
√ can initialize the client
√ can query the Kubernetes API

kubernetes-version
------------------
√ is running the minimum Kubernetes API version
√ is running the minimum kubectl version

linkerd-config
--------------
√ control plane Namespace exists
√ control plane ClusterRoles exist
√ control plane ClusterRoleBindings exist
√ control plane ServiceAccounts exist
√ control plane CustomResourceDefinitions exist
√ control plane MutatingWebhookConfigurations exist
√ control plane ValidatingWebhookConfigurations exist
√ control plane PodSecurityPolicies exist

linkerd-existence
-----------------
√ 'linkerd-config' config map exists
√ heartbeat ServiceAccount exist
√ control plane replica sets are ready
√ no unschedulable pods
√ controller pod is running
√ can initialize the client
√ can query the control plane API

linkerd-api
-----------
√ control plane pods are ready
√ control plane self-check
√ [kubernetes] control plane can talk to Kubernetes
√ [prometheus] control plane can talk to Prometheus
√ no invalid service profiles

linkerd-version
---------------
√ can determine the latest version
√ cli is up-to-date

control-plane-version
---------------------
√ control plane is up-to-date
√ control plane and cli versions match

Status check results are √```

### Environment

- Kubernetes Version:
```
version.Info{Major:"1", Minor:"13+", GitVersion:"v1.13.7-gke.24", GitCommit:"2ce02ef1754a457ba464ab87dba9090d90cf0468", GitTreeState:"clean", BuildDate:"2019-08-12T22:05:28Z", GoVersion:"go1.11.5b4", Compiler:"gc", Platform:"linux/amd64"}
```
- Cluster Environment: GKE
- Host OS: GKE COS
- Linkerd version: edge-19.10.1

### Possible solution

### Additional context

The issue concerns the deployment's “live calls” view and its success-rate calculation. Reproduce it by sending many requests to a meshed service on a nonexistent path, then trace how 4xx responses are accounted for. Done means 404 responses reduce the displayed success rate; no file or test is named in the report.

Written by the indexing model from the issue text.