When an executor or administrator is adjudged trustee on account of goods, effects or credits in his hands or possession merely as executor or administrator in an action originally commenced against him as a trustee, or against the deceased, the execution shall not be served on his own goods or estate or on his person; but he is liable for the amount in his hands, in like manner and to the same extent only, as he would have been to the principal defendant if there had been no trustee process.