kernel/v2: a host always exists, remove dumb check

plugins/kernel_v2/config/vm.rb

@@ -455,13 +455,9 @@ module VagrantPlugins
         end
 
         if has_nfs
-          if !machine.env.host
-            errors << I18n.t("vagrant.config.vm.nfs_requires_host")
-          else
           errors << I18n.t("vagrant.config.vm.nfs_not_supported") if \
             !machine.env.host.capability(:nfs_installed)
         end
-        end
 
         # Validate networks
         has_fp_port_error = false

templates/locales/en.yml

@@ -877,9 +877,6 @@ en:
           that `nfsd` is installed on your machine, and try again. If you're
           on Windows, NFS isn't supported. If the problem persists, please
           contact Vagrant support.
-        nfs_requires_host: |-
-          Using NFS shared folders requires a host to be specified
-          using `config.vagrant.host`.
         network_ip_ends_in_one: |-
           Static IPs cannot end in ".1" since that address is always
           reserved for the router. Please use another ending.