Network proxy settings does not keep "DIRECT" value in apt.conf when set back to method "None"

Network proxy settings in gnome-control-center removes Acquire::*::proxy::HOST "DIRECT" value when set proxy method "None".

NOTE: Acquire::*::proxy::HOST "DIRECT" works as no_proxy for APT.

How to reproduce:
  1. open network settings in gnome-control-center
  2. set proxy like the example below:
      * method - manual
      * HTTP Proxy - example.com:8080
      * HTTPS Proxy - example.com:8090
  3. press "Apply system wide"
      - confirm proxy settings are written in /etc/apt/apt.conf
  4. add the line below into /etc/apt/apt.conf manually
      - Acquire::http::proxy::server1.local "DIRECT";
  5. add the line below into /etc/apt/apt.conf.d/90no-proxy.conf
      - Acquire::http::proxy::server2.local "DIRECT";
  6. turn off proxy by set back the Method to "None" and press "Apply system wide" again.

Expected to happen:
  7. the three lines below are removed from /etc/apt/apt.conf
          - Acquire::http::proxy "http://example.com:8080/";
          - Acquire::https::proxy "http://example.com:8080/";
          - Acquire::ftp::proxy "http://example.com:8080/";
     but leave the lines below in /etc/apt/apt.conf and /etc/apt/apt.conf.d/90no-proxy.conf as is to be useful for the next time.
          - Acquire::http::proxy::server1.local "DIRECT";
          - Acquire::http::proxy::server2.local "DIRECT";

What happened instead:
  7. the three lines are removed and also "DIRECT" lines are removed.

NOTE:
"Apply system wide" for /etc/environment leave no_proxy value as is.

ProblemType: BugDistroRelease: Ubuntu 11.10
Package: gnome-control-center 1:3.2.0-0ubuntu6
ProcVersionSignature: Ubuntu 3.0.0-12.20-generic 3.0.4
Uname: Linux 3.0.0-12-generic x86_64
ApportVersion: 1.23-0ubuntu3
Architecture: amd64
CasperVersion: 1.285
Date: Tue Oct 18 05:07:00 2011
LiveMediaBuild: Ubuntu 11.10 "Oneiric Ocelot" - Release amd64 (20111011)
ProcEnviron:
 LANG=en_US.UTF-8
 SHELL=/bin/bashSourcePackage: gnome-control-center
UpgradeStatus: No upgrade log present (probably fresh install)
usr_lib_gnome-control-center:
 deja-dup 20.0-0ubuntu3
 gnome-bluetooth 3.2.0-0ubuntu1
 indicator-datetime 0.3.0-0ubuntu3