abandon reference iscsitarget

This version of the reference iscsitarget achieve a read, found only
reference to the SCSI command processing part is not enough, you must
reference iscsitarget in command of receiving and processing threads are
fused in, and that there is a big conflict with the method itself
receives command processing, therefore abandon this method to be
implemented in SCST, the method in SCST reference Qlogic implemented.

这个版本参考iscsitarget实现读操作，发现仅仅参考SCSI的命令处理部分是不够的，必须将iscsitarget中对命令的接收和处理线程也融合进来，而这将与本身的接收命令处理方法存在较大冲突，因此放弃此方法，改为在SCST中实现，参考Qlogic在SCST中实现的方法。