Merge pull request #44968 from MrHohn/kube-proxy-healthcheck

Automatic merge from submit-queue (batch tested with PRs 44727, 45409, 44968, 45122, 45493)

Separate healthz server from metrics server in kube-proxy

From #14661, proposal is on kubernetes/community#552.

Couple bullet points as in commit:
- /healthz will be served on 0.0.0.0:10256 by default.
- /metrics and /proxyMode will be served on port 10249 as before.
- Healthz handler will verify timestamp in iptables mode.

/assign @nicksardo @bowei @thockin 

**Release note**:

```release-note
NONE
```

test/e2e/framework/networking_utils.go

@@ -273,8 +273,8 @@ func (config *NetworkingTestConfig) DialFromNode(protocol, targetIP string, targ
 // GetSelfURL executes a curl against the given path via kubectl exec into a
 // test container running with host networking, and fails if the output
 // doesn't match the expected string.
-func (config *NetworkingTestConfig) GetSelfURL(path string, expected string) {
-	cmd := fmt.Sprintf("curl -q -s --connect-timeout 1 http://localhost:10249%s", path)
+func (config *NetworkingTestConfig) GetSelfURL(port int32, path string, expected string) {
+	cmd := fmt.Sprintf("curl -i -q -s --connect-timeout 1 http://localhost:%d%s", port, path)
 	By(fmt.Sprintf("Getting kube-proxy self URL %s", path))
 
 	// These are arbitrary timeouts. The curl command should pass on first try,