buffet: Allow buffet to talk to web server using D-Bus

We are moving privet code into buffet.

BUG=brillo:1161
TEST=./build_packages --board=gizmo

Change-Id: I8974f6398011a9f08e619c45d888a222a7c21bfd
Reviewed-on: https://chromium-review.googlesource.com/276600
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Reviewed-by: Vitaly Buka <vitalybuka@chromium.org>
Commit-Queue: Vitaly Buka <vitalybuka@chromium.org>
Tested-by: Vitaly Buka <vitalybuka@chromium.org>

buffet/etc/dbus-1/org.chromium.Buffet.conf

diff --git a/buffet/etc/dbus-1/org.chromium.Buffet.conf b/buffet/etc/dbus-1/org.chromium.Buffet.conf
index de9e4c5..23a4ffc 100644
--- a/buffet/etc/dbus-1/org.chromium.Buffet.conf
+++ b/buffet/etc/dbus-1/org.chromium.Buffet.conf
@@ -13,4 +13,9 @@
   <policy user="buffet">
     <allow own="org.chromium.Buffet" />
   </policy>
+
+  <policy user="webservd">
+        <allow send_destination="org.chromium.Buffet"
+               send_interface="org.chromium.WebServer.RequestHandler"/>
+  </policy>
 </busconfig>