Fix classpath for X-Pack scripts on Windows

With the move of X-Pack to a module, the classpath for the scripts needs
to be adjusted. This was done on Unix, but not for Windows. This commit
addresses Windows.

x-pack/plugin/core/src/main/bin/x-pack-env.bat

@@ -2,4 +2,4 @@ rem Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 rem or more contributor license agreements. Licensed under the Elastic License;
 rem you may not use this file except in compliance with the Elastic License.
 
-set ES_CLASSPATH=!ES_CLASSPATH!;!ES_HOME!/plugins/x-pack/x-pack-core/*
+set ES_CLASSPATH=!ES_CLASSPATH!;!ES_HOME!/modules/x-pack/x-pack-core/*

x-pack/plugin/security/src/main/bin/x-pack-security-env.bat

@@ -4,4 +4,4 @@ rem you may not use this file except in compliance with the Elastic License.
 
 call "%~dp0x-pack-env.bat" || exit /b 1
 
-set ES_CLASSPATH=!ES_CLASSPATH!;!ES_HOME!/plugins/x-pack/x-pack-security/*
+set ES_CLASSPATH=!ES_CLASSPATH!;!ES_HOME!/modules/x-pack/x-pack-security/*