refactor: Add client host keys without prompting
refactor: Add client host keys without prompting

If client host keys are not present in either '/root/.ssh/known_hosts'
or '~/.ssh/known_hosts' they will be added without a prompt (a message
will be printed to stdout).

Prompting is left in place in the event of conflicting host keys.

open-power-ref-design-toolkit/cluster-genesis,open-power-ref-design-toolkit/cluster-genesis