Clarify general override policy for config parameters
Clarify general override policy for config parameters

Especially point out that config parameters that have a list of values
are always completely overridden and it's not possible to just add a
value to an inherited list.

Signed-off-by: Edwin Kempin <d43fb6c98c97e553b671ed9a9318100f1de386e7@google.com>
Change-Id: I52a909320bd71f176e38f76b3536bfb827b9252e

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