Instance metadata variables are not expanded

Ref: https://github.com/harvester/harvester/issues/2342

Verify Steps:

Install Harvester with any nodes
Create Image for VM creation
Create VM with following CloudConfig

## template: jinja
#cloud-config
package_update: true
password: password
chpasswd: { expire: False }
sshpwauth: True
write_files:
  - content: |
      #!/bin/bash
      vmName=$1
      echo "VM Name is: $vmName" > /home/cloudinitscript.log      
    path: /home/exec_initscript.sh
    permissions: '0755'
runcmd:
  - - systemctl
    - enable
    - --now
    - qemu-guest-agent.service
  - - echo
    - "{{ ds.meta_data.local_hostname }}"
  - - /home/exec_initscript.sh
    - "{{ ds.meta_data.local_hostname }}"
packages:
  - qemu-guest-agent

login to the VM
- file /home/exec_initscript.sh should exists
- file /home/cloudinitscript.log should exists
- execute cat /home/cloudinitscript.log, VM name should be the same as the VM.