Fix to remove duplicate contact based on their push-params

Merged Anthony Gauchy requested to merge fix/duplicate_push_contact_2_0 into release/2.0

(Backport) If duplicate contact (based on their push params) exist they are removed from DB (at biding for internalDB, filtered at fetching with Redis). Tests with internalDB and Redis. (only on 2.1, see 3be2ef09)

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