make test less time sensitive

Seen fail on travis:

**   c1    2.7 === expect resp.status == 200
**** c1    2.7 EXPECT resp.status (200) == "200" match
**   c1    2.7 === expect resp.http.Age == 1
---- c1    2.7 EXPECT resp.http.Age (2) == "1" failed

bin/varnishtest/tests/s00006.vtc

@@ -21,7 +21,7 @@ client c1 {
 	expect resp.status == 200
 	expect resp.http.Age == 0
 
-	delay 1.0
+	delay 0.2
 
 	txreq -url "/"
 	rxresp