Finish hooking up hv.enable_virtualization_extensions

plugins/providers/hyperv/action/import.rb

@@ -147,7 +147,7 @@ module VagrantPlugins
           options[:auto_start_action] = auto_start_action if auto_start_action
           options[:auto_stop_action] = auto_stop_action if auto_stop_action
           options[:differencing_disk] = differencing_disk if differencing_disk
-          options[:enable_virtualization_extensions] = enable_virtualization_extensions if enable_virtualization_extensions
+          options[:enable_virtualization_extensions] = "$True" if enable_virtualization_extensions and enable_virtualization_extensions == true
 
           env[:ui].detail("Creating and registering the VM...")
           server = env[:machine].provider.driver.import(options)

plugins/providers/hyperv/config.rb

@@ -14,6 +14,7 @@ module VagrantPlugins
       attr_accessor :differencing_disk # Create differencing disk instead of cloning whole VHD [Boolean]
       attr_accessor :auto_start_action #action on automatic start of VM. Values: Nothing, StartIfRunning, Start
       attr_accessor :auto_stop_action #action on automatic stop of VM. Values: ShutDown, TurnOff, Save
+      attr_accessor :enable_virtualization_extensions # Enable virtualization extensions (nested virtualization). Values: true, false
 
       def initialize
         @ip_address_timeout = UNSET_VALUE

plugins/providers/hyperv/scripts/import_vm_xml.ps1

@@ -11,7 +11,7 @@ Param(
     [string]$vmname=$null,
     [string]$auto_start_action=$null,
     [string]$auto_stop_action=$null,
-    [bool]$enable_virtualization_extensions=$False
+    [string]$enable_virtualization_extensions=$False
 )
 
 # Include the following modules