webos-{init,shutdown}scripts: Change PACKAGE_ARCH to MACHINE_ARCH

:Release Notes:
Depends on formerly TUNE_PKGARCH now MACHINE_ARCH fbprogress/upstart
so it cannot have "all" architecture.

:Detailed Notes:

:Testing Performed:
Build tested and verified with sstate-diff-machines.sh.

:QA Notes:
No change to image.

:Issues Addressed:
[GF-44050] allarch components have different signatures with different
           tcmode

Open-webOS-DCO-1.0-Signed-off-by: Martin Jansa <martin.jansa@lge.com>

Change-Id: Ieac179a428e869d4514fda099a0e4b355b4a4d66
Reviewed-on: https://g2g.palm.com/4107
Reviewed-by: DCO Verification
Build: Martin Jansa <Martin.Jansa@lge.com>
Reviewed-by: Martin Jansa <Martin.Jansa@lge.com>
Tested-by: Martin Jansa <Martin.Jansa@lge.com>
Reviewed-by: Susan Montooth <susan.montooth@lge.com>