Upgrade konnectivity-client for GRPC connection fixes

The v0.0.19 Konnectivity client includes several
significant fixes to prevent the GRPC tunnel between
the KAS and the APIServer Network Proxy from becoming
blocked/wedged.
Importantly it picks up the fix for kubernetes-sigs/apiserver-network-proxy#167.
We believe this will also fix many of the failures currently seen on
https://testgrid.k8s.io/sig-api-machinery-network-proxy#ci-kubernetes-e2e-gci-gce-network-proxy-grpc&width=5.

cluster/gce/addons/konnectivity-agent/konnectivity-agent-ds.yaml

@@ -25,7 +25,7 @@ spec:
       nodeSelector:
         kubernetes.io/os: linux
       containers:
-        - image: k8s.gcr.io/kas-network-proxy/proxy-agent:v0.0.15
+        - image: k8s.gcr.io/kas-network-proxy/proxy-agent:v0.0.19
           name: konnectivity-agent
           command: ["/proxy-agent"]
           args: [

cluster/gce/manifests/konnectivity-server.yaml

@@ -20,7 +20,7 @@ spec:
       {{ disallow_privilege_escalation}}
       {{ capabilities }}
         {{ drop_capabilities }}
-    image: k8s.gcr.io/kas-network-proxy/proxy-server:v0.0.15
+    image: k8s.gcr.io/kas-network-proxy/proxy-server:v0.0.19
     resources:
       requests:
         cpu: 25m