Make MethodUtils CACHE_METHODS volatile (1.X) (#416)

written under the class monitor but read lock-free in getCachedMethod and cacheMethod, so setCacheMethods(false) may not be visible to other threads

Author: rootvector2

src/main/java/org/apache/commons/beanutils/MethodUtils.java

@@ -126,7 +126,7 @@ public int hashCode() {
      * which may introduce memory-leak problems.
      * </p>
      */
-    private static boolean CACHE_METHODS = true;
+    private static volatile boolean CACHE_METHODS = true;
 
     /** An empty class array */
     private static final Class<?>[] EMPTY_CLASS_PARAMETERS = new Class[0];