Use nginx user in harvester-cluster-repo image

[brandboat]

Problem:
This is an enhancement, use nginx instead of root user in harvester-cluster-repo image.

Solution:
Use nginx user in harvester-cluster-repo

Related Issue:

Test plan:

1. make ci to build iso, and prepare a single node harvester cluster (easy for testing)
2. Enable addon (e.g. pcidevices-controller) and the addon could be successfully installed.
3. Go inside harvester-cluster-repo pod and check if user is nginx (we can use k9s shell shortcut s to go inside each pod)

[brandboat]

@mergify backport v1.3 v1.4

[mergify]

backport v1.3 v1.4

✅ Backports have been created

• #850 Use nginx user in harvester-cluster-repo image (backport #849) has been created for branch v1.3
• #851 Use nginx user in harvester-cluster-repo image (backport #849) has been created for branch v1.4