"n been sold under a contract of conditional sale reserving title poss°s'sfon in the vendor, may be attached as if unencumbered; and the mortgagee, pledgee, lienor or conditional vendor, or his assigns, may be summoned in the same action in which the property is attached as the trustee of the mortgagor, pledgor, lienee or conditional vendee, or his assigns, to answer such"