webos-image: libxml=v2.9.1

:Release Notes:
Upgrade libxml from 2.7.8 to 2.9.1

:Detailed Notes:

:Testing Performed:
BHV-190 contains performance testing results with 2.9.1:
avg - 0.916
median - 0.926
stdev - 0.026
min - 0.827
max - 0.935

:QA Notes:

:Issues Addressed:
[BHV-190] Upgrade libxml2 from 2.7.8 to 2.9.1
[BHV-1078] CCC: libxml=2.9.1

Open-webOS-DCO-1.0-Signed-off-by: Kyrylo Kropivyanskiy <kyrylo.kropivyanskiy@lge.com>

Change-Id: I3d525607284f9d93d6ed78872d094907dc2f2d66
Reviewed-on: https://g2g.palm.com/4773
Reviewed-by: DCO Verification
Reviewed-by: Susan Montooth <susan.montooth@lge.com>
Tested-by: Susan Montooth <susan.montooth@lge.com>