network: reduce dial timeout in discoverer test

We don't care much about dialing, but the same constant is used in outer
discoverer loop in case no connections are established and we have no
connections established.

pkg/network/discovery_test.go

@@ -56,7 +56,7 @@ func (ft *fakeTransp) Close() {
 func TestDefaultDiscoverer(t *testing.T) {
 	ts := &fakeTransp{}
 	ts.dialCh = make(chan string)
-	d := NewDefaultDiscovery(nil, time.Second/2, ts)
+	d := NewDefaultDiscovery(nil, time.Second/16, ts)
 
 	var set1 = []string{"1.1.1.1:10333", "2.2.2.2:10333"}
 	sort.Strings(set1)