Relax known host name checking

For sshkey distribution. (#269)

At first encounter, a user whishing to connect to a host needs to confirm the identity (fingerprint) of the target host.
We do automate this procedure for git (see https://github.com/cargomedia/puppet-packages/blob/master/modules/github/manifests/knownhost.pp) but there, we kinda know the fingerprint for `github.com`

With puppetdb we would otherwise have to store (export) a host's fingerprint and realize (read) it on a sshkeys user wanting to access a machine.. We thought it's easier to just not enforce the known host policy.

@njam @tomaszdurka what do you guys think?