Section 6A. No surety shall be required upon bonds filed by national banks, located in the commonwealth and duly permitted to act in a fiduciary capacity, as receiver, assignee, guardian, conservator except that the court appointing such a bank as such a fiduciary, other than as trustee, may upon application of an interested person require the bank so appointed to give such security, in addition to the lien or security provided by the laws of the United States, as the court may consider proper, and upon failure of such bank to give the security required may revoke such appointment and remove such bank.