webos-image: Update layer pins for 2014-03-14

meta-webos-backports as of 2014-03-14 10:30:30 -0700

687c409 webos-image: libxml=v2.9.1

meta-webos as of 2014-03-14 10:37:27 -0700

f5f177c meta-webos: pmloglib=52,v3.1.0
1e101f0 meta-webos: libpbnjson=30,v2.5.0 luna-service2=176,v3.7.0

Open-webOS-DCO-1.0-Signed-off-by: Susan Montooth <susan.montooth@lge.com>

Change-Id: I8ff7a65ed2fd6c8cc390ef3b2a3a8e296d5a201b
Reviewed-on: https://g2g.palm.com/4946
Reviewed-by: DCO Verification
Build: Susan Montooth <susan.montooth@lge.com>
Reviewed-by: Build Verification
Reviewed-by: Susan Montooth <susan.montooth@lge.com>
Tested-by: Susan Montooth <susan.montooth@lge.com>