change nds2AddJava to prioritze existing nds2.jar in javaclasspath

At present nds2AddJava will only use an existing nds2.jar in the javaclasspath if the nds2 client-config doesn't work or NDS2_JAR_PATH is not set. Instead, use existing nds2.jar if already in path, then NDS2_JAR_PATH if it exists, then client-config result.