test-e2e.sh: idempotently and safely create test ns if not exists (carvel-dev#295)

* test-e2e.sh: idempotently and safely create test ns if not exists

* hack/test-e2e: now with more accurate comments

Author: joe-kimmel-vmw

hack/test-e2e.sh

@@ -4,6 +4,8 @@ set -e -x -u
 
 go clean -testcache
 
+# create ns if not exists because the `apply -f -` won't complain on a no-op if the ns already exists.
+kubectl create ns $KAPPCTRL_E2E_NAMESPACE --dry-run=client -o yaml | kubectl apply -f -
 go test ./test/e2e/ -timeout 60m -test.v $@
 
 echo E2E SUCCESS