webos: Use stronger override for opkglibdir
webos: Use stronger override for opkglibdir

* bbappend expects this set consistently, so we don't support
  setting different value e.g. in local.conf
* this is part of bigger DISTRO conf cleanup

[GF-2417] Reorganize distro configs

Open-webOS-DCO-1.0-Signed-off-by: Martin Jansa <77d25b640e536c950b8ae8cdd4f0574e3b263d04@palm.com>
Change-Id: I5970185694088c275c9da7d116a7e99446861c46
Reviewed-on: https://g2g.palm.com/1603
Reviewed-by: Martin Jansa <77d25b640e536c950b8ae8cdd4f0574e3b263d04@palm.com>
Tested-by: Martin Jansa <77d25b640e536c950b8ae8cdd4f0574e3b263d04@palm.com>
Reviewed-by: Keith Derrick <62fb45708ac3f392369421d5b0d5e49e3fca4211@lge.com>
Reviewed-by: Herb Kuta <b3a29751759f7c347ddccce0da8ed5b3d511fcd0@lge.com>
Reviewed-by: Susan Montooth <be0b8b1fe2cc6a744be9b1ae6516e077aa323e09@lge.com>

openwebos/meta-webos,openwebos/meta-webos,nizovn/meta-webos-ports,openwebos/meta-webos,openwebos/meta-webos,nizovn/meta-webos-ports,Garfonso/meta-webos-ports,Garfonso/meta-webos-ports