[HUDI-2321] Use the caller classloader for ReflectionUtils (#3535)

Based on the discussion on stackoverflow:
https://stackoverflow.com/questions/1771679/difference-between-threads-context-class-loader-and-normal-classloader

The Thread.currentThread().getContextClassLoader() should never be used
because the context classloader is not immutable, user can overwrite it
when thread switches, it is also nullable.

The objection here: https://stackoverflow.com/a/36228195 says the
Thread.currentThread().getContextClassLoader() is a JDK design error
and the context classloader is never suggested to be used. The API that
needs classloader should ask the user to set up the right classloader.

hudi-common/src/main/java/org/apache/hudi/common/util/ReflectionUtils.java

@@ -51,8 +51,7 @@ public class ReflectionUtils {
     synchronized (CLAZZ_CACHE) {
       if (!CLAZZ_CACHE.containsKey(clazzName)) {
         try {
-          Class<?> clazz = Class.forName(clazzName, true,
-              Thread.currentThread().getContextClassLoader());
+          Class<?> clazz = Class.forName(clazzName);
           CLAZZ_CACHE.put(clazzName, clazz);
         } catch (ClassNotFoundException e) {
           throw new HoodieException("Unable to load class", e);