Enable batch record usage in logexpect

This enables catching batch related log problems using logexpect.

This commit will make several test cases start failing until #1588 has been fixed.

bin/varnishtest/vtc_logexp.c

@@ -330,7 +330,8 @@ logexp_start(struct logexp *le)
 	}
 	le->vsl = VSL_New();
 	AN(le->vsl);
-	c = VSL_CursorVSM(le->vsl, le->vsm, le->d_arg ? 0 : VSL_COPT_TAIL);
+	c = VSL_CursorVSM(le->vsl, le->vsm,
+	    (le->d_arg ? 0 : VSL_COPT_TAIL) | VSL_COPT_BATCH);
 	if (c == NULL) {
 		vtc_log(le->vl, 0, "VSL_CursorVSM: %s", VSL_Error(le->vsl));
 		logexp_close(le);