Wait before exiting testWidgets (#174)

* Wait a few seconds for test cleanup on Windows testWidgets

The testWidgets() test fails consistently on ci.jenkins.io since the
transition from Azure to AWS.  Since the tests are already using long
sleep calls for various other purposes, let's sleep at the exit from
the failing test so that there is time for Java to close files.

Testing done

Confirmed that `mvn clean verify` passes on my Linux computer.  Rely on
ci.jenkins.io to confirm the fix works on Windows.

* Try a 5 second sleep

The 3 second sleep was enough in 3 of 4 test runs.  Let's see if a 5
second sleep improves the failure rate.

Author: MarkEWaite

src/test/java/org/jenkinsci/plugins/matrixauth/Security2180Test.java

@@ -8,6 +8,7 @@
 import static org.junit.Assert.assertTrue;
 
 import com.cloudbees.hudson.plugins.folder.Folder;
+import hudson.Functions;
 import hudson.model.Cause;
 import hudson.model.Executor;
 import hudson.model.FreeStyleBuild;
@@ -292,6 +293,10 @@ public void testWidgets() throws Exception {
         final HtmlPage htmlPage = webClient.goTo("");
         final String contentAsString = htmlPage.getWebResponse().getContentAsString();
         assertThat(contentAsString, not(containsString("job/folder/job/job"))); // Fails while unfixed
+        if (Functions.isWindows()) {
+            // Wait several seconds so that files are closed before test cleanup
+            Thread.sleep(5000);
+        }
     }
 
     @Test