Update framework to use jetty-server 9.4 (#11272)

Fix upload issue

pom.xml

@@ -47,8 +47,8 @@
 
         <!-- Dependency unpack directory -->
         <dependency.unpack.directory>${project.build.directory}/dependency-unpack</dependency.unpack.directory>
-        
-        <jetty.version>9.2.26.v20180806</jetty.version>
+ 
+        <jetty.version>9.4.12.v20180830</jetty.version>
 
         <!-- Sonar properties -->
         <sonar.java.source>8</sonar.java.source>

server/src/main/java/com/vaadin/server/communication/FileUploadHandler.java

@@ -617,6 +617,7 @@ public class FileUploadHandler implements RequestHandler {
             } finally {
                 session.unlock();
             }
+            return true;
             // Note, we are not throwing interrupted exception forward as it is
             // not a terminal level error like all other exception.
         } catch (final Exception e) {

uitest/src/test/java/com/vaadin/tests/components/upload/InterruptUploadTest.java

@@ -1,9 +1,10 @@
 package com.vaadin.tests.components.upload;
 
-import com.vaadin.testbench.elements.LabelElement;
-import com.vaadin.testbench.elements.WindowElement;
-import com.vaadin.tests.tb3.MultiBrowserTest;
-import com.vaadin.tests.util.LoremIpsum;
+import java.io.BufferedWriter;
+import java.io.File;
+import java.io.FileWriter;
+import java.io.IOException;
+
 import org.junit.Test;
 import org.openqa.selenium.By;
 import org.openqa.selenium.JavascriptExecutor;
@@ -12,10 +13,10 @@ import org.openqa.selenium.internal.WrapsElement;
 import org.openqa.selenium.remote.LocalFileDetector;
 import org.openqa.selenium.remote.RemoteWebElement;
 
-import java.io.BufferedWriter;
-import java.io.File;
-import java.io.FileWriter;
-import java.io.IOException;
+import com.vaadin.testbench.elements.LabelElement;
+import com.vaadin.testbench.elements.WindowElement;
+import com.vaadin.tests.tb3.MultiBrowserTest;
+import com.vaadin.tests.util.LoremIpsum;
 
 import static org.junit.Assert.assertTrue;