Ensure 'helm repo add' is also not pollute on helmfile template (#1887)

When having multiple helmfiles in one helmfile.d folder and multiple of
them having repositories defined, the errors mention in #1749 still
existed.

Fixes #1749 (again)

Signed-off-by: Matthias Baur <m.baur@syseleven.de>

test/integration/test-cases/issue-1749/input/helmfile.d/helmfile1.yaml.gotmpl

@@ -1,3 +1,7 @@
+repositories:
+- name: bitnami
+  url: https://charts.bitnami.com/bitnami
+
 releases:
   - name: test1
     chart: ../../../../charts/raw

test/integration/test-cases/issue-1749/input/helmfile.d/helmfile2.yaml.gotmpl

@@ -1,3 +1,7 @@
+repositories:
+- name: prometheus-community
+  url: https://prometheus-community.github.io/helm-charts
+
 releases:
   - name: test2
     chart: ../../../../charts/raw