Have default names for primary and non-primary disks

plugins/kernel_v2/config/disk.rb

@@ -105,16 +105,14 @@ module VagrantPlugins
           @primary = false
         end
 
-        # Give the disk a default name if unset
-        # TODO: Name not required if primary?
-        if @primary
-          base_name = "vagrant_primary"
-        else
-          base_name = "vagrant"
+        if @name == UNSET_VALUE
+          if @primary
+            @name = "vagrant_primary"
+          else
+            @name = "name_#{@type.to_s}_#{@id.split("-").last}"
+          end
         end
 
-        @name = "#{base_name}_#{@type.to_s}_#{@id.split("-").last}" if @name == UNSET_VALUE
-
         @provider_config = nil if @provider_config == {}
       end