vtc: Stabilize v56

The probe timeout is irrelevant, especially under load. And to be
certain, we can witness probe updates to ensure we are testing VCL
with a system in the expected state.

bin/varnishtest/tests/v00056.vtc

@@ -26,7 +26,7 @@ varnish v1 -vcl {
 
 	probe foo {
 		.url = "/";
-		.timeout = 1s;
+		.timeout = 1m;
 		.interval = 1s;
 		.window = 3;
 		.threshold = 2;
@@ -56,18 +56,30 @@ client c1 {
 	expect resp.status == 500
 } -run
 
+logexpect l1 -v v1 -g raw -q Backend_health {
+	expect 0 0 Backend_health "default Still sick"
+} -start
+
 barrier b1 sync
 barrier b2 sync
 
+logexpect l1 -wait
+
 client c2 {
 	txreq
 	rxresp
 	expect resp.status == 500
 } -run
 
+logexpect l2 -v v1 -g raw -q Backend_health {
+	expect 0 0 Backend_health "default Went healthy"
+} -start
+
 barrier b3 sync
 barrier b4 sync
 
+logexpect l2 -wait
+
 client c3 {
 	txreq
 	rxresp