[digital ocean|compute] pass '1' instead of true for scrub

see also: cb95e27c8a (commitcomment-4959542)

lib/fog/digitalocean/requests/compute/destroy_server.rb

@@ -12,7 +12,7 @@ module Fog
             :method   => 'GET',
             :path     => "droplets/#{id}/destroy",
             # We scrub data so future users can't read our disks.
-            :query    => {:scrub_data => true,},
+            :query    => {:scrub_data => '1' },
           )
         end