[Android]fix storage 异步执行导致service执行异常的问题

android/sdk/src/main/java/com/taobao/weex/appfram/storage/DefaultWXStorage.java

@@ -143,20 +143,21 @@ public void run() {
 
     @Override
     public void close() {
+        final ExecutorService needCloseService = mExecutorService;
         execute(new Runnable() {
             @Override
             public void run() {
                 try {
                     mDatabaseSupplier.closeDatabase();
-                    if (mExecutorService != null) {
-                        mExecutorService.shutdown();
-                        mExecutorService = null;
+                    if (needCloseService != null) {
+                        needCloseService.shutdown();
                     }
                 } catch (Exception e) {
                     WXLogUtils.e(WXSQLiteOpenHelper.TAG_STORAGE, e.getMessage());
                 }
             }
         });
+        mExecutorService = null;
     }
 
     private boolean performSetItem(String key, String value, boolean isPersistent, boolean allowRetryWhenFull) {