Reduce cache expiry

Reduce cache expiry to help support issues where a function
may be scaled down by a user, when it is still in use.

The 5s cache meant that all requests would fail until the
expiry. The 250ms setting is a 20x reduction.

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <[email protected]>

gateway/main.go

@@ -144,7 +144,7 @@ func main() {
 		MaxPollCount:         uint(1000),
 		SetScaleRetries:      uint(20),
 		FunctionPollInterval: time.Millisecond * 100,
-		CacheExpiry:          time.Second * 5, // freshness of replica values before going stale
+		CacheExpiry:          time.Millisecond * 250, // freshness of replica values before going stale
 		ServiceQuery:         externalServiceQuery,
 	}