mcf: Use REMOTE variable instead of "origin" (v4.0.4)

:Release Notes:
Allow to use different remote name than "origin".

:Detailed Notes:
Remote name should eventually be configureable in weboslayers.py, but
for start allow at least to set it globally in one place in mcf script.

:Testing Performed:
Only build tested.

:QA Notes:
No change to image.

:Issues Addressed:
[ES-451] mcf: should update remote URL when it's changed in
         weboslayers.py

Open-webOS-DCO-1.0-Signed-off-by: Martin Jansa <martin.jansa@lge.com>
Change-Id: Ic74721df72ef39a5d8f329b1f7a840e407e20f1a
Reviewed-on: https://g2g.palm.com/4994
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: Build Verification
Reviewed-by: Susan Montooth <susan.montooth@lge.com>