Fix apply upgrade

Executing the test with this command:

$ adt-run -B --unbuilt-tree=. --setup-commands 'mount -o remount,rw /' --setup-commands 'apt-add-repository -y ppa:barry/systemimage' --setup-commands 'apt-get --no-list-cleanup update -o Dir::Etc::SourceList=/dev/null' --setup-commands 'apt-get install -y -q system-image-cli system-image-common system-image-dbus' --setup-commands 'if [ ! -d "/etc/system-image/config.d" ]; then mkdir -p /etc/system-image/config.d && cd /etc/system-image && ln -sf ../client.ini config.d/00_default.ini && ln -sf ../channel.ini config.d/01_channel.ini; fi' --setup-commands 'sync; sleep 2; mount -o remount,ro /' --output /tmp/ota --- ssh -s ./adb-reboot-to-recovery

Fixes the issue and the upgrade is applied correctly. The difference is that, instead of copying the system-image config files from /etc/system-image to /etc/system-image/config.d, that command makes symbolic links from the files in /etc/system-image/config.d to the files in /etc/system-image.

It seems that si requires the files at config /etc/system-image/config.d (or in aa custom directory passed by -C) but when the upgrade is applied it modifies the old config files, the ones at /etc/system-image, and the new version installed is not being reported properly.

In other words, the upgrade was being applied but the installed version wasn't being reported correctly.

This makes sense, since we still haven't updated the server to create the config files in the new location. That's the last major blocker before we can land si 3.0 in vivid and other channels.

Fix committed into lp:ubuntu-ota-tests at revision 17, scheduled for release in ubuntu-ota-tests, milestone Unknown