Add test for create secret

Signed-off-by: Somtochi Onyekwere <somtochionyekwere@gmail.com>

cmd/flux/testdata/create_secret/helm/secret-helm.yaml

@@ -0,0 +1,10 @@
+---
+apiVersion: v1
+kind: Secret
+metadata:
+  name: helm-secret
+  namespace: my-namespace
+stringData:
+  password: my-password
+  username: my-username
+