Move imports to top-level

Signed-off-by: Zack Cerza <zack.cerza@inktank.com>
Fix a circular import

Signed-off-by: Zack Cerza <zack.cerza@inktank.com>
Ignore the exit code of ssh-keyscan

Signed-off-by: Zack Cerza <zack.cerza@inktank.com>