Work around kubectl exec failures by enabling StreamingProxyRedirects

[Cynerva]

Workaround for https://bugs.launchpad.net/bugs/1940527.

This is kicking the can down the road to CK 1.24 and we will need to get to the bottom of it sooner or later. But at least we can unblock 1.22.

[Cynerva]

Before and after:

$ kubectl exec ubuntu -- whoami
error: unable to upgrade connection: unable to upgrade: missing upgrade headers in request: http.Header{"Connection":[]string{"close", "Upgrade"}, "Content-Length":[]string{"0"}, "Kubectl-Command":[]string{"kubectl exec"}, "Kubectl-Session":[]string{"558e825c-5b41-4d75-8f62-bc4e554604be"}, "Upgrade":[]string{"SPDY/3.1"}, "User-Agent":[]string{"kubectl/v1.22.0 (linux/amd64) kubernetes/c2b5237"}, "X-Forwarded-For":[]string{"10.172.69.252, 10.246.154.51, 10.246.154.107"}, "X-Forwarded-Proto":[]string{"https"}, "X-Real-Ip":[]string{"10.172.69.252"}, "X-Stream-Protocol-Version":[]string{"v4.channel.k8s.io"}}

$ juju upgrade-charm kubernetes-master --path /home/gkk/work/charm-builds/kubernetes-master
Added  charm "kubernetes-master", revision 0, to the model
Leaving endpoints in "alpha": aws, aws-iam, azure, ceph-client, ceph-storage, certificates, cni, container-runtime, coordinator, dns-provider, etcd, gcp, grafana, ha, keystone-credentials, kube-api-endpoint, kube-control, kube-masters, loadbalancer, loadbalancer-external, loadbalancer-internal, nrpe-external-master, openstack, prometheus, vault-kv, vsphere

$ kubectl exec ubuntu -- whoami
root

[kwmonroe]

Nice find!