Description of problem:
On Fedora 15, setting a proxy using the GNOME network settings has no effect on Thunderbird.

Version-Release number of selected component (if applicable):
thunderbird-3.1.9-6.fc15.x86_64

How reproducible:
This seems to be always reproducible when trying to set a SOCKS proxy to use.
Setting other proxy types doesn't seem to work either, although I haven't tried
those thoroughly.

Steps to Reproduce (generic):
1. Click on the NetworkManager icon and click 'Network Settings'.
2. Go to the 'Network proxy' settings.
3. Set the proxy method to 'Manual'.
4. Type the hostname and port of your proxy in the appropriate field.
5. Start Thunderbird (set to use system proxy settings under the advanced network preferences).

Actual results:
Thunderbird tries to connect to the internet without using a proxy.

Expected results:
Thunderbird should connect through the proxy specified in the network settings.

Additional info:
It seems that this issue is affecting a number of applications, which still attempt to fetch proxy settings from gconf instead of the new dconf backend.