INT 2F U - NETWORK REDIRECTOR - CLOSE REMOTE FILE
        AX = 1106h
        ES:DI -> SFT
            SFT DPB field -> DPB of drive containing file
Return: CF set on error
            AX = DOS error code (see INT 21/AH=59h)
        CF clear if successful
            SFT updated (redirector must decrement open count, which may be
                        done with INT 2F/AX=1208h)
Note:   called by DOS 3.1+ kernel
SeeAlso: AX=1208h,AX=1227h,INT 21/AH=3Eh