Classic confinement allows the snap to behave like a traditionally
packaged application with full access to the system, and enables the
use of traditional directories such as /etc and /var/log.
We will continue to store all of the snap's files in $SNAP* directories.
This enables the snap to cleanup after itself if it is removed. However,
traditional directory locations are symlinked to their corresponding
$SNAP* directories.
For example, nova configs are installed in $SNAP_COMMON/etc/nova
which has a symlink at /etc/nova.
The nova apps then use the traditional directories when running
commands and services.
Change-Id: Ie21c66007a37b90ac3bca042505bad332fa76543
1388b583b5