New test: install the operator without default runtimeClass

[wainersm]

Test Case

Use case: As an user installing CoCo via operator, I don't want it to deploy a default "kata" runtimeclass .

Add a new test case to the operator tests to check the condition defaultRuntimeClassName is omitted.

Split out of #247

Implementation

1. Change the kustomization file on the corresponding ccruntime's overlay directory. For example, in the default ccruntime kustomization file:

diff --git a/config/samples/ccruntime/default/kustomization.yaml b/config/samples/ccruntime/default/kustomization.yaml
index b22bc16..286ef44 100644
--- a/config/samples/ccruntime/default/kustomization.yaml
+++ b/config/samples/ccruntime/default/kustomization.yaml
@@ -30,7 +30,7 @@ patches:
         snapshotter: "nydus"
     - op: add
       path: /spec/config/defaultRuntimeClassName
-      value: "kata-qemu"
+      value: ""
     - op: add
       path: /spec/config/debug
       value: false

2. Install the operator
3. Check the default runtime "kata" is not created.