Fix compiler warning/error under gcc7

Gcc7 complains about falling through from the previous case to the default arm

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

test-tool/iscsi-support.c

@@ -2939,8 +2939,6 @@ void populate_ident_tgt_desc(unsigned char *buf, struct scsi_device *dev)
                                         tgt_desig = desig;
                                         prev_type = desig->designator_type;
                                 }
-                        default:
-                                continue;
                 }
         }
         if (tgt_desig == NULL) {