fix proxy redirect (http status 302) response

fixes http://mantis.tokeek.de/view.php?id=517

The url given in bug report uses a gzip input stream which causes the HTTPClient.writeto() throw an IOException due to incomplete input stream. This in turn prevents the 302 reponse to the client browser. 
By limiting to serve target content just on httpstatus=200 will proxy the header reponse and client browsers redirect settings can be honored.

source/net/yacy/http/ProxyHandler.java

@@ -225,9 +225,12 @@ public class ProxyHandler extends AbstractRemoteHandler implements Handler {
                 convertHeaderToJetty(clientresponse, response);
                 response.setStatus(statusCode);
                 
-    			client.writeTo(response.getOutputStream());
+                if (statusCode == HttpServletResponse.SC_OK) { // continue to serve header to client e.g. HttpStatus = 302 (while skiping content)
+                    client.writeTo(response.getOutputStream()); // may throw exception on httpStatus=302 while gzip encoded inputstream
                 }
-		} catch(final SocketException se) {
+
+            }
+            } catch (final SocketException se) {
                 throw new ServletException("Socket Exception: " + se.getMessage());
             } finally {
                 client.finish();

source/net/yacy/server/http/HTTPDProxyHandler.java

@@ -66,6 +66,7 @@ import java.util.logging.FileHandler;
 import java.util.logging.Level;
 import java.util.logging.LogManager;
 import java.util.logging.Logger;
+import javax.servlet.http.HttpServletResponse;
 
 import net.yacy.cora.document.id.DigestURL;
 import net.yacy.cora.protocol.ClientIdentification;
@@ -572,8 +573,9 @@ public final class HTTPDProxyHandler {
                                 " StoreHTCache=" + storeHTCache +
                                 " SupportError=" + supportError);
 
-//                        FileUtils.copy(res.getDataAsStream(), outStream);
-                        client.writeTo(outStream);
+                        if (statusCode == HttpServletResponse.SC_OK) { // continue to serve header to client e.g. HttpStatus = 302 (while skiping content)
+                            client.writeTo(outStream); // may throw exception on httpStatus=302 while gzip encoded inputstream
+                        }
 
                         conProp.put(HeaderFramework.CONNECTION_PROP_PROXY_RESPOND_CODE,"TCP_MISS");
                     }