Add -f to cp command for multus-installer

[tjwallace]

Description of the change
Handle case when the dest file is busy.

See k8snetworkplumbingwg/multus-cni#1221 (comment)

Benefits
No manual intervention required if a node crashes.

Possible drawbacks
N/A

Checklist

• Title of the PR conforms to the Conventional Commits standard.
• Scope of the of the PR title contains the chart name.
• Chart version in Chart.yaml has been bumped according to Semantic Versioning.
• Chart artifacthub.io/changes changelog annotation has been updated in Chart.yaml. See Artifact Hub documentation for more info.
• Variables have been documented in the values.yaml file.

[angelnu]

Thanks