Stop swallowing exceptions that happen in TestEnvironment.dispose

This commit is excepted to reveal bogus tests that do not properly shutdown,
especially on Windows where directory cannot be removed if there are any running processes
that use it as a working directory.

src/main/java/org/jvnet/hudson/test/JenkinsRule.java

@@ -509,21 +509,19 @@ public void after() throws Exception {
 
             try {
                 env.dispose();
-            } catch (Exception x) {
-                x.printStackTrace();
-            }
-
-            // Hudson creates ClassLoaders for plugins that hold on to file descriptors of its jar files,
-            // but because there's no explicit dispose method on ClassLoader, they won't get GC-ed until
-            // at some later point, leading to possible file descriptor overflow. So encourage GC now.
-            // see http://bugs.sun.com/view_bug.do?bug_id=4950148
-            // TODO use URLClassLoader.close() in Java 7
-            System.gc();
-
-            // restore defaultUseCache
-            if(Functions.isWindows()) {
-                URLConnection aConnection = new File(".").toURI().toURL().openConnection();
-                aConnection.setDefaultUseCaches(origDefaultUseCache);
+            } finally {
+                // Hudson creates ClassLoaders for plugins that hold on to file descriptors of its jar files,
+                // but because there's no explicit dispose method on ClassLoader, they won't get GC-ed until
+                // at some later point, leading to possible file descriptor overflow. So encourage GC now.
+                // see http://bugs.sun.com/view_bug.do?bug_id=4950148
+                // TODO use URLClassLoader.close() in Java 7
+                System.gc();
+
+                // restore defaultUseCache
+                if(Functions.isWindows()) {
+                    URLConnection aConnection = new File(".").toURI().toURL().openConnection();
+                    aConnection.setDefaultUseCaches(origDefaultUseCache);
+                }
             }
         }
     }