Review fixes for async-http-client-1-common:javaagent (open-telemetry#17268)

Co-authored-by: otelbot <197425009+otelbot@users.noreply.github.com>

Author: otelbot[bot]

instrumentation/async-http-client/async-http-client-1-common/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/asynchttpclient/common/AsyncHttpClientHelper.java

@@ -33,6 +33,7 @@ public interface AsyncHttpClientHelper {
    * @param request the HTTP request
    * @return the server port
    */
+  @Nullable
   Integer getServerPort(Request request);
 
   /**

instrumentation/async-http-client/async-http-client-1-common/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/asynchttpclient/common/AsyncHttpClientHttpAttributesGetter.java

@@ -55,6 +55,7 @@ public String getServerAddress(Request request) {
   }
 
   @Override
+  @Nullable
   public Integer getServerPort(Request request) {
     return helper.getServerPort(request);
   }

instrumentation/async-http-client/async-http-client-1-common/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/asynchttpclient/common/ResponseInstrumentation.java

@@ -17,6 +17,7 @@
 import io.opentelemetry.context.Scope;
 import io.opentelemetry.javaagent.extension.instrumentation.TypeInstrumentation;
 import io.opentelemetry.javaagent.extension.instrumentation.TypeTransformer;
+import javax.annotation.Nullable;
 import net.bytebuddy.asm.Advice;
 import net.bytebuddy.description.type.TypeDescription;
 import net.bytebuddy.matcher.ElementMatcher;
@@ -63,7 +64,7 @@ public static Scope onEnter(
     }
 
     @Advice.OnMethodExit(onThrowable = Throwable.class, suppress = Throwable.class)
-    public static void onExit(@Advice.Enter Scope scope) {
+    public static void onExit(@Advice.Enter @Nullable Scope scope) {
       if (null != scope) {
         scope.close();
       }
@@ -88,7 +89,7 @@ public static Scope onEnter(
     }
 
     @Advice.OnMethodExit(onThrowable = Throwable.class, suppress = Throwable.class)
-    public static void onExit(@Advice.Enter Scope scope) {
+    public static void onExit(@Advice.Enter @Nullable Scope scope) {
       if (null != scope) {
         scope.close();
       }