<!-- If you need to report a security issue please visit https://github.com/apache/dubbo/security/policy -->

ExtensionLoader cannot be resumed after interruption.

```
java.lang.InterruptedException
  at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(AbstractQueuedSynchronizer.java:1302)
  at java.util.concurrent.CountDownLatch.await(CountDownLatch.java:231)
  at org.apache.dubbo.common.utils.ClassLoaderResourceLoader.loadResources(ClassLoaderResourceLoader.java:55)
  at org.apache.dubbo.common.extension.ExtensionLoader.loadDirectory(ExtensionLoader.java:1005)
  at org.apache.dubbo.common.extension.ExtensionLoader.loadDirectory(ExtensionLoader.java:943)
  at org.apache.dubbo.common.extension.ExtensionLoader.loadExtensionClasses(ExtensionLoader.java:931)
  at org.apache.dubbo.common.extension.ExtensionLoader.getExtensionClasses(ExtensionLoader.java:913)
  at org.apache.dubbo.common.extension.ExtensionLoader.createExtension(ExtensionLoader.java:752)
  at org.apache.dubbo.common.extension.ExtensionLoader.getExtension(ExtensionLoader.java:548)
  at org.apache.dubbo.common.extension.ExtensionLoader.getExtension(ExtensionLoader.java:523)
  at org.apache.dubbo.rpc.protocol.injvm.InjvmInvoker.<init>(InjvmInvoker.java:74)
```
/**
     * Return default extension name, return <code>null</code> if not configured.
     */
    public String getDefaultExtensionName() {
        getExtensionClasses();
        return cachedDefaultName;
    }
    /**
     * Register new extension via API
     *
     * @param name  extension name
     * @param clazz extension class
     * @throws IllegalStateException when extension with the same name has already been registered.
     */
    public void addExtension(String name, Class<?> clazz) {
        checkDestroyed();
        getExtensionClasses(); 
        if (!type.isAssignableFrom(clazz)) {
            throw new IllegalStateException("Input type " +
                clazz + " doesn't implement the Extension " + type);
        }
        if (clazz.isInterface()) {
            throw new IllegalStateException("Input type " +
                clazz + " can't be interface!");
        }
        if (!clazz.isAnnotationPresent(Adaptive.class)) {
            if (StringUtils.isBlank(name)) {
                throw new IllegalStateException("Extension name is blank (Extension " + type + ")!");
            }
            if (cachedClasses.get().containsKey(name)) {