local.conf: Convert variables set by mcf to use weak assignment
local.conf: Convert variables set by mcf to use weak assignment

:Release Notes:
Convert local.conf variables set by mcf to use weak assignment. This
will allow them to use overridden in webos-local.conf and
webos-global.conf without having to resort to using the
_forcevariable override.

:Detailed Notes:
The one exception is MACHINE, as it shouldn't be overridden in
webos-*.conf . Note that the OPENWEBOS_GIT_REPO setting in local.conf
will be overridden by the assignment in webos-repositories.inc.

Also removed the COVERAGE_BUILD setting, as it appears nowhere in the
current metadata.

:Testing Performed:
Verified overrides occurred when variables are defined in
webos-local.conf and webos-global.conf .

:QA Notes:

:Issues Addressed:
[ES-978] Convert local.conf variables set by mcf to use weak assignment

Open-webOS-DCO-1.0-Signed-off-by: Martin Jansa <martin.jansa@lge.com>
Change-Id: Idf094fa48ce2fd8822189617c66e55c1b947c7bc
Reviewed-on: https://g2g.palm.com/6150
Reviewed-by: DCO Verification
Build: Martin Jansa <516df3ff67e1fa5d153800b15fb204c0a1a389dc@lge.com>
Reviewed-by: Martin Jansa <516df3ff67e1fa5d153800b15fb204c0a1a389dc@lge.com>
Tested-by: Martin Jansa <516df3ff67e1fa5d153800b15fb204c0a1a389dc@lge.com>
Reviewed-by: Build Verification
Reviewed-by: Susan Montooth <be0b8b1fe2cc6a744be9b1ae6516e077aa323e09@lge.com>

hyunkim9123/build-webos,openwebos/build-webos,aeg-aeg/mywebOS,openwebos/build-webos,aeg-aeg/mywebOS,hyunkim9123/build-webos