BUG: Make manta config show resiliant to network errors

[Masber]

Imagine a user starts using manta and they don't know which site is manta configured with. The next step would be to run manta config show or inspect the configuration file manually (more troublesome). If manta does not have access to keycloak API, then it won't show an error, but the user still does not know to which site is manta pointing to, this is inefficient and manta should instead show the information it has access to even if network is down.