meta-ros-common: drop dunfell and add hardknott to ROS_OE_RELEASE_SERIES
meta-ros-common: drop dunfell and add hardknott to ROS_OE_RELEASE_SERIES

* now with separate branch for dunfell, gatesgarth and hardknott (master) we don't need
  to keep dunfell here in master branch and we can add hardknott in preparation
  for next OE 3.3 Hardknott release like meta-oe did this time:
  https://git.openembedded.org/meta-openembedded/commit/?id=8fbaa7e41cc30dcffc82447c780b456119541029

Signed-off-by: Martin Jansa <77d25b640e536c950b8ae8cdd4f0574e3b263d04@lge.com>

bmwcarit/meta-ros,bmwcarit/meta-ros,bmwcarit/meta-ros,bmwcarit/meta-ros