Fix failing tests in witness mode

The simple fact that Witness records might show up in the log might
break logexpect commands. There's no reason why we'd want to expect
Witness records since their purpose is to be checked after the test
finishes.

bin/varnishtest/vtc_logexp.c

@@ -281,7 +281,7 @@ logexp_dispatch(struct VSL_data *vsl, struct VSL_transaction * const pt[],
 			data = VSL_CDATA(t->c->rec.ptr);
 			len = VSL_LEN(t->c->rec.ptr) - 1;
 
-			if (tag == SLT__Batch)
+			if (tag == SLT__Batch || tag == SLT_Witness)
 				continue;
 
 			ok = 1;