Section 17. Money paid with the approval of the judge of probate to a corporation qualified to act in the commonwealth in guaranteeing the fidelity of persons and in acting as surety on bonds, or to any person for acting as surety on any official bond given to such probate court, may be allowed as a charge against the estate and in the case of trusteeship shall be a charge against principal, except that if and so long as the trust estate shall consist wholly of real estate the money so paid shall be a charge against income.