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, neutron configs are installed in $SNAP_COMMON/etc/neutron
which has a symlink at /etc/neutron.
The neutron apps then use the traditional directories when running
commands and services.
Change-Id: I392ba95cfaad1509b58beb2f82ba865b73971d5a
fd1265eb20