Add unit tests for export

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

cmd/flux/testdata/export/helm-repo.yaml

@@ -0,0 +1,11 @@
+---
+apiVersion: source.toolkit.fluxcd.io/v1beta1
+kind: HelmRepository
+metadata:
+  name: flux-system
+  namespace: {{ .fluxns }}
+spec:
+  interval: 5m0s
+  timeout: 1m0s
+  url: https://stefanprodan.github.io/podinfo
+