Fix CNI integration test (linkerd#7660)

Reverts the change made to `env_vars.sh` in linkerd#7541

That file is consumed by `docker run --env-file` which requires the old
format, as documented [here](https://docs.docker.com/engine/reference/commandline/run/#set-environment-variables--e---env---env-file).

Also renamed it to `env_vars.list` to have it not mistaken to be a shell
target.

This broke the `ARM64 integration test` as seen here:
https://github.com/linkerd/linkerd2/runs/4887813913?check_suite_focus=true#step:7:34

Author: alpeb

cni-plugin/test/data/env_vars.list

@@ -0,0 +1,21 @@
+KUBE_DNS_SERVICE_PORT=53
+KUBE_DNS_PORT_53_TCP_PROTO=tcp
+KUBE_DNS_PORT_53_UDP=udp://10.110.0.10:53
+KUBE_DNS_PORT_53_UDP_PROTO=udp
+KUBERNETES_PORT_443_TCP_PROTO=tcp
+KUBERNETES_PORT_443_TCP_ADDR=10.110.0.1
+KUBE_DNS_PORT_53_UDP_ADDR=10.110.0.10
+KUBERNETES_PORT=tcp://10.110.0.1:443
+KUBE_DNS_PORT_53_TCP_ADDR=10.110.0.10
+KUBE_DNS_PORT=udp://10.110.0.10:53
+KUBERNETES_SERVICE_PORT_HTTPS=443
+KUBERNETES_PORT_443_TCP_PORT=443
+KUBERNETES_PORT_443_TCP=tcp://10.110.0.1:443
+KUBE_DNS_PORT_53_TCP_PORT=53
+KUBE_DNS_PORT_53_TCP=tcp://10.110.0.10:53
+KUBERNETES_SERVICE_PORT=443
+KUBE_DNS_SERVICE_PORT_DNS=53
+KUBE_DNS_SERVICE_PORT_DNS_TCP=53
+KUBERNETES_SERVICE_HOST=10.110.0.1
+KUBE_DNS_PORT_53_UDP_PORT=53
+KUBE_DNS_SERVICE_HOST=10.110.0.10

cni-plugin/test/data/env_vars.sh

@@ -141,7 +141,7 @@ func startDocker(testNum int, wd string, testWorkRootDir string, tempCNINetDir s
 		"-v", tempCNINetDir + ":" + hostCniNetDir,
 		"-v", tempCNIBinDir + ":/host/opt/cni/bin",
 		"-v", tempK8sSvcAcctDir + ":/var/run/secrets/kubernetes.io/serviceaccount",
-		"--env-file", wd + "/data/env_vars.sh",
+		"--env-file", wd + "/data/env_vars.list",
 		"-e", cniNetworkConfigName,
 		"-e", "SLEEP=true",
 	}