Avoid `unless`

templates/guests/debian/network_dhcp.erb

@@ -2,7 +2,7 @@
 # The contents below are automatically generated by Vagrant. Do not modify.
 auto eth<%= options[:interface] %>
 iface eth<%= options[:interface] %> inet dhcp
-<% unless options[:use_dhcp_assigned_default_route] %>
+<% if !options[:use_dhcp_assigned_default_route] %>
     post-up route del default dev $IFACE
 <% end %>
 #VAGRANT-END