Pin Kind node image used in EphemeralCluster

By default, `kind` would install a node image for Kubernetes 1.24, which
is a couple minor versions past what we deploy to cloud environments and
which runs afoul of some Terraform bugs[1]. Pin the Kind node image we
use to a Kubernetes 1.22 image, to match the Kind we use in other CI
contexts.

[1]: hashicorp/terraform-provider-kubernetes#1724

janus_core/src/test_util/kubernetes.rs

@@ -32,6 +32,8 @@ impl EphemeralCluster {
                 &kubeconfig_path.to_string_lossy(),
                 "--name",
                 &cluster_name,
+                "--image",
+                "kindest/node:v1.22.9@sha256:8135260b959dfe320206eb36b3aeda9cffcb262f4b44cda6b33f7bb73f453105",
             ])
             .stdin(Stdio::null())
             .stdout(Stdio::null())