Refactor some importprunedfunds checks with guard clause
Refactor some importprunedfunds checks with guard clause

Credit to jkczyz


Former-commit-id: 795e8448a684f10037b00178b65d83effcc0471f
syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin