TESTS: move the default url, lun and iscsi context into a structure

Signed-off-by: Ronnie Sahlberg <ronniesahlberg@gmail.com>

test-tool/test_write16_wrprotect.c

@@ -44,7 +44,7 @@ test_write16_wrprotect(void)
 	if (!inq->protect || (rc16 != NULL && !rc16->prot_en)) {
 		logging(LOG_VERBOSE, "Device does not support/use protection information. All commands should fail.");
 		for (i = 1; i < 8; i++) {
-			ret = write16(iscsic, tgt_lun, 0,
+			ret = write16(sd->iscsi_ctx, sd->iscsi_lun, 0,
 				      block_size, block_size,
 				      i, 0, 0, 0, 0, buf,
 				      EXPECT_INVALID_FIELD_IN_CDB);