replace depreciated HTTPClient setStaleConnectionCheckEnabled with setValidateAfterInactivity()

source/net/yacy/cora/protocol/http/HTTPClient.java

@@ -149,8 +149,6 @@ public class HTTPClient {
         builder.setConnectTimeout(default_timeout);
         // SO_TIMEOUT: maximum period inactivity between two consecutive data packets in milliseconds
         builder.setSocketTimeout(default_timeout);
-		// getting an I/O error when executing a request over a connection that has been closed at the server side
-		builder.setStaleConnectionCheckEnabled(true);
         // ignore cookies, cause this may cause segfaults in default cookiestore and is not needed
         builder.setCookieSpec(CookieSpecs.IGNORE_COOKIES);
         builder.setRedirectsEnabled(true);
@@ -209,7 +207,7 @@ public class HTTPClient {
         // Increase max connections for localhost
         final HttpHost localhost = new HttpHost(Domains.LOCALHOST);
         pooling.setMaxPerRoute(new HttpRoute(localhost), maxcon);
-		
+        pooling.setValidateAfterInactivity(default_timeout); // on init set to default 5000ms
         final SocketConfig socketConfig = SocketConfig.custom()
                 // Defines whether the socket can be bound even though a previous connection is still in a timeout state.
                 .setSoReuseAddress(true)