fixes#3083
Detect the presence of the default DHCP server that comes in a fresh
VirtualBox install and clean it up to prevent it from colliding with
Vagrant-managed network config.
In order to accomplish this, we:
- add a `remove_dhcp_server` call to the virtualbox driver
- fix dhcp options parsing to allow `:dhcp_{ip,lower,upper}`
configuration options to make it through (so a user can override the
removal behavior with some explicit configuration)
- add the full `:network_name` to the details returned from
`:read_dhcp_servers`, so we can have a durable value to pass to
`:remove_dhcp_server`
Note that we do have to eat one more `VBoxManage list dhcpservers` for
each network interface to support this, but this seemed like a nominal
cost
This is just a refactor, no behavior change.
Instead of stitching together dhcpserver info in the structure returned
from `read_host_only_interfaces`, sprout a new driver method called
`read_dhcp_servers` to return that information separately.
This means that driver clients (well there's really only _one_ client in
`ProviderVirtualBox::Action::Network`) have to do a bit more work to get
interface and DHCP server information.
But this gives us (a) a cleaner and more consistent driver interface and
(b) groundwork for a fix for #3083, which will require interacting with
DHCP servers outside of the context of host-only interfaces.
Paul Hinze