bug 981447 - use more conservative dns caching values r=sworkman a=dougt

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extra : rebase_source : 4d63155c64e5cceb3cd43c33c2ab97eccc1225cf
bug 981513 - revert 807441 r=sworkman a=dougt

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extra : rebase_source : 0e6a74426e6ea90c792250bb03b961f5b01333ef