deb packages support: switch from /var/dpkg to /var/lib/dpkg

deb packages support: switch from /var/dpkg to /var/lib/dpkg

OE generally tries to use /var/dpkg, but the change is missing
in some places, so it is needed to move completely to one of the
options. Keeping the dpkg's default /var/lib/dpkg causes less
maintenance overhead for OE.

Signed-off-by: Filip Zyzniewski <filip.zyzniewski@gmail.com>
Signed-off-by: Tom Rini <tom_rini@mentor.com>