lbi: Add --remove-signatures to install time lbi copy

[ckyrouac]

We are unable to copy a signed image from c/storage -> c/storage while preserving the signature. See
containers/image#2599

fixes #812

[cgwalters]

• Downloading successful, but checksum doesn't match. Calculated: ef16d195332d673efbe2fc9a316726df177a605e1caef3ca49f88a7181f973654347400cb50ee464dd7206fc9a59c34cf37d0baea158add0bde531cb7cab8039(sha512) Expected: b2b0cdc3fdc6021ff6ddd33a4b508daa7050cc8cdfca7dd9aa6c854ed80dd39b4fd5bfa6e66db2c37e0ad25cee9f53e7b24b84d7f302f2ca07198439524d1c99(sha512)

CI is failing on rpm-md repository metadata desynchronization. It's exactly stuff like this that would be greatly mitigated if we put rpms in registries instead.

[cgwalters]

@ckyrouac I know we'd had flakes in the integration tests lately but this one looks to have introduced this:

Trying to pull registry.redhat.io/ubi9/podman:latest...
Error: initializing source docker://registry.redhat.io/ubi9/podman:latest: unable to retrieve auth token: invalid username/password: unauthorized: Please login to the Red Hat Registry using your Customer Portal credentials. Further instructions can be found here: https://access.redhat.com/RegistryAuthentication

So we'll need to set up a pull secret to make this work.

[ckyrouac]

ah, I'll try to find a good signed image from an unauthenticated repo, or I'll just push a signed test image to a public quay repo