Make MethodUtils CACHE_ENABLED volatile (#414)

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

Author: rootvector2

src/main/java/org/apache/commons/beanutils2/MethodUtils.java

@@ -118,7 +118,7 @@ public String toString() {
      * would mean having a map keyed by context classloader which may introduce memory-leak problems.
      * </p>
      */
-    private static boolean CACHE_ENABLED = true; //NOPMD @GuardedBy("this")
+    private static volatile boolean CACHE_ENABLED = true; //NOPMD volatile: written under the class monitor, read lock-free in computeIfAbsent
 
     /**
      * Stores a cache of MethodKey -> Method.