Move all writable data used by security-manager and appfw to /var

The purpose of these changes is to make OSTree and AppFw update domains
compatible with each other. Some intergation code is also needed to deploy
initial data to writable area (see SPEC-359 in Jira).

Bug-AGL: SPEC-359

Change-Id: Iccba1e9916c569167df2922ad5e2d90cc33f06fe
Signed-off-by: Anton Gerasimov <anton@advancedtelematic.com>
Signed-off-by: Stephane Desneux <stephane.desneux@iot.bzh>