Add Runnable overrides to ease use of Java 8 language features

Runnable and Callable are both @FunctionalInterfaces. The difference is
that Callable requires a return value whereas Runnable does not, so in
situations where we don't care about a return value, rather than having to
add an unnecessary 'return null;' at the end of the lambda, we can simply
use a non-returning Runnable instead.

Unfortunately, owing to legacy reasons, Runnable is not declared to throw
checked exceptions whereas Callable is, so in situations where checked
exceptions are thrown we still need to have a 'return null;' call at the
end.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=172935400

java/google/registry/rde/RdeReporter.java

@@ -44,7 +44,6 @@ import java.io.ByteArrayInputStream;
 import java.net.MalformedURLException;
 import java.net.SocketTimeoutException;
 import java.net.URL;
-import java.util.concurrent.Callable;
 import javax.inject.Inject;
 
 /**
@@ -81,21 +80,20 @@ public class RdeReporter {
     req.addHeader(new HTTPHeader(AUTHORIZATION, "Basic " + token));
     req.setPayload(reportBytes);
     logger.infofmt("Sending report:\n%s", new String(reportBytes, UTF_8));
-    HTTPResponse rsp = retrier.callWithRetry(
-        new Callable<HTTPResponse>() {
-          @Override
-          public HTTPResponse call() throws Exception {
-            HTTPResponse rsp = urlFetchService.fetch(req);
-            switch (rsp.getResponseCode()) {
-              case SC_OK:
-              case SC_BAD_REQUEST:
-                break;
-              default:
-                throw new UrlFetchException("PUT failed", req, rsp);
-            }
-            return rsp;
-          }
-        }, SocketTimeoutException.class);
+    HTTPResponse rsp =
+        retrier.callWithRetry(
+            () -> {
+              HTTPResponse rsp1 = urlFetchService.fetch(req);
+              switch (rsp1.getResponseCode()) {
+                case SC_OK:
+                case SC_BAD_REQUEST:
+                  break;
+                default:
+                  throw new UrlFetchException("PUT failed", req, rsp1);
+              }
+              return rsp1;
+            },
+            SocketTimeoutException.class);
 
     // Ensure the XML response is valid.
     XjcIirdeaResult result = parseResult(rsp);