Liquidate: Vault variables storage update

Finally, all that’s left to do for this liquidate function is to update total vault supply and debt by lowering the liquidated amounts.

Note that vaultVariables will already contain updated branch data info after liquidation.

After we perform the update, we emit the LogLiquidate event with liquidated amounts:

emit LogLiquidate(msg.sender, actualColAmt_, actualDebtAmt_, to_);