default.xml: default to jethro branch and use master selectively
default.xml: default to jethro branch and use master selectively

the manifest is supposed to track the 'stable' branch of OE layers. We only want
to use master for a selected number of layers.

Change-Id: I2c5b2021b22459de61e66ace98ae1c68c195edc2
Signed-off-by: Nicolas Dechesne <05fca36dfcf68f7e1c9eaf62b074676ab50a133b@linaro.org>

ndechesne/qcom-oe-manifest,96boards/oe-rpb-manifest,linaro-home/lhg-oe-manifests