In the absence of the /etc/guix/channels.scm file, %default-channels is used
anyway. If user manually (or by extra-special-file) created the file, we
should respect it. This commit therefore changes the default to #f, hopefully
having zero impact on people not actively using the `channels' field.
* gnu/services/base.scm (<guix-configuration>)[channels]: Set default to #f.
Change-Id: I516c1735a037a153fabbebfc337051aaf0be2155
Signed-off-by: Ludovic Courtès <ludo@gnu.org>
