target: check for XCOPY parameter truncation

Check for XCOPY header, CSCD descriptor and segment descriptor list
truncation, and respond accordingly.

SPC4r37 6.4.1 EXTENDED COPY(LID4) states (also applying to LID1 reqs):
  If the parameter list length causes truncation of the parameter list,
  then the copy manager shall transfer no data and shall terminate the
  EXTENDED COPY command with CHECK CONDITION status, with the sense key
  set to ILLEGAL REQUEST, and the additional sense code set to PARAMETER
  LIST LENGTH ERROR.

This behaviour can be tested using the libiscsi ExtendedCopy.ParamHdr
test.

Signed-off-by: David Disseldorp <ddiss@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>