To use systemd user mode from recipes, it convenient that
some variables are available, which point proper paths for unit files.
For that, backport 2 variables which has been added latest poky.
(From Poky rev:
319a69f1d757a577b50a2ca9c8fbf845eba8e274)
When upgrading poky in future, these variables should be removed
from poky-agl.conf.
Change-Id: I8ba7594b488ecd6421caf7dde484eb6b091ff0de
Signed-off-by: Tadao Tanikawa <tanikawa.tadao@jp.panasonic.com>