INT 2F - DR-DOS 6.0 TaskMAX - CHECK IF TASK RUNNING PRIMARY COMMAND INTERPRETER
        AX = 270Dh
        DX = task index
Return: DX = status
            0000h if primary command interpreter (COMMAND.COM, etc.) running
            0001h if not in root shell for task
Note:   TaskMAX will return 0001h if the specified task has spawned another
          command interpreter with AX=2707h
SeeAlso: AX=270Ch