Return 1 to VSL_Dispatch on completing the test script.

Return 1 on completing the test script. This will prevent the API from
reporting any more transactions matching the query, which would
trigger an assert.

bin/varnishtest/vtc_logexp.c

@@ -247,7 +247,7 @@ logexp_dispatch(struct VSL_data *vsl, struct VSL_transaction * const pt[],
 				logexp_next(le);
 				if (le->test == NULL)
 					/* End of test script */
-					return (0);
+					return (1);
 			}
 			if (skip)
 				le->skip_cnt++;