feat: better object creation in "k8s start"

When running "tutor k8s start", it's unnecessary to attempt to create volumes
and namespace multiple times.

CHANGELOG.md

@@ -4,6 +4,8 @@ Note: Breaking changes between versions are indicated by "💥".
 
 ## Unreleased
 
+- [Improvement] Better Kubernetes object creation.
+
 ## v11.3.0 (2021-05-18)
 
 - 💥[Security] Disable python-evaluated input by default as we don't run codejail.

tutor/commands/k8s.py

@@ -239,8 +239,7 @@ def start(context: Context) -> None:
         "--kustomize",
         tutor_env.pathjoin(context.root),
         "--selector",
-        # Here use `notin (job, xxx)` when there are other components to ignore
-        "app.kubernetes.io/component!=job",
+        "app.kubernetes.io/component notin (job,volume,namespace)",
     )