Normalise a user-supplied confirmationLookBackLevels, falling back to
DEFAULT_CONFIRMATION_LOOKBACK_LEVELS when it is absent or not a
usable non-negative number. Shared by Operation and WalletOperation so
the two confirmation loops cannot drift apart.
Normalise a user-supplied
confirmationLookBackLevels, falling back to DEFAULT_CONFIRMATION_LOOKBACK_LEVELS when it is absent or not a usable non-negative number. Shared byOperationandWalletOperationso the two confirmation loops cannot drift apart.