test_extendedcopy_descr_limits: Fix a crash if this command is not supported

Avoid that this test crashes as follows if the RECEIVE COPY RESULTS
command is not supported:

    [FAILED] RECEIVECOPYRESULT command failed with sense. (null)
Segmentation fault

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Sushma Gurram <Sushma.Gurram@sandisk.com>

test-tool/test_extendedcopy_descr_limits.c

@@ -66,7 +66,7 @@ test_extendedcopy_descr_limits(void)
 	logging(LOG_VERBOSE, "Issue RECEIVE COPY RESULTS (OPERATING PARAMS)");
 	ret = receive_copy_results(sd, SCSI_COPY_RESULTS_OP_PARAMS, 0,
 			(void **)&opp, EXPECT_STATUS_GOOD);
-	if (ret == -2) {
+	if (ret < 0) {
 		CU_PASS("[SKIPPED] Target does not support "
 				"RECEIVE_COPY_RESULTS. Skipping test");
 		return;