Prevent race condition in JettyConnector

Signed-off-by: Jan Supol <jan.supol@oracle.com>
diff --git a/connectors/jetty-connector/src/main/java/org/glassfish/jersey/jetty/connector/JettyConnector.java b/connectors/jetty-connector/src/main/java/org/glassfish/jersey/jetty/connector/JettyConnector.java
index 2acd645..48a5394 100644
--- a/connectors/jetty-connector/src/main/java/org/glassfish/jersey/jetty/connector/JettyConnector.java
+++ b/connectors/jetty-connector/src/main/java/org/glassfish/jersey/jetty/connector/JettyConnector.java
@@ -436,7 +436,9 @@
                 @Override
                 public void onComplete(final Result result) {
                     entityStream.closeQueue();
-                    callback.response(jerseyResponse.get());
+                    if (!callbackInvoked.get()) {
+                        callback.response(jerseyResponse.get());
+                    }
                     responseFuture.complete(jerseyResponse.get());
                 }
 
diff --git a/pom.xml b/pom.xml
index 688ef91..929949f 100644
--- a/pom.xml
+++ b/pom.xml
@@ -2155,7 +2155,7 @@
         <jaxrs.api.spec.version>2.1</jaxrs.api.spec.version>
         <jaxrs.api.impl.version>2.1.6</jaxrs.api.impl.version>
         <jetty.plugin.version>6.1.26</jetty.plugin.version>
-        <jetty.version>9.4.27.v20200227</jetty.version>
+        <jetty.version>9.4.28.v20200408</jetty.version>
         <jetty.servlet.api.25.version>6.1.14</jetty.servlet.api.25.version>
         <jsonb.api.version>1.0.2</jsonb.api.version>
         <jsonp.ri.version>1.1.6</jsonp.ri.version>