Fix singleargo secret copying

[mbaldessari]

To do this we actually parse the set of value files (and extraParams) and
we verify if global.singleArgoCD is true or not.

If it is true there is no need to copy the git secret to the namespaced
argo instance as there is only a single "clusterwide" argo instance.

Tested as follows:

    1. No secrets public repo single argo  -> OK
    2. No secrets public repo multi argo   -> OK
    3. One secret private repo single argo -> OK
    ```
    ./pattern.sh make TARGET_ORIGIN=mcg-private-http TOKEN_SECRET=private-repo TOKEN_NAMESPACE=openshift-operators install
    ```

    4. One secret private repo multi argo  -> OK
    ```
    ./pattern.sh make TARGET_ORIGIN=mcg-private-http TOKEN_SECRET=private-repo TOKEN_NAMESPACE=openshift-operators install
    ```

Fixes: #838

[openshift-ci]

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