Remove permissions issue docs with persistent Host client using Docker.

[johnnymatthews]

There's an issue in the Hosts repo to fix the permissions issue when spinning up a Host via Docker with persistent storage: shinzonetwork/shinzo-host-client#303

Once that's fixed and merged, we should remove the warnings we have in /hosts/install/.

[johnnymatthews]

Currently blocked by shinzonetwork/shinzo-host-client#303. That issue needs to be fixed before we can merge #302.