fix vars name error

Signed-off-by: Yanan Shen <yanans@vmware.com>

windows/windows_update_install/prepare_msu_file.yml

@@ -55,7 +55,7 @@
     win_execute_cmd_no_log: "{{ hide_secrets | default(false) }}"
     win_powershell_cmd: >-
       {{ win_nfs_mount_cmd }};
-      $file = Get-ChildItem -Path {{ msu_file_nfs_path }} | where Name -like '{{ msu_file_reg }}';
+      $file = Get-ChildItem -Path {{ msu_file_nfs_path }} | where Name -like '{{ msu_file_name_reg }}';
       if ($file) {Copy-Item -Path $file.FullName -Destination {{ msu_dest_dir }} -ErrorAction Stop;};
       net use {{ drive_letter_new }}: /delete