ovs: Update prebuilt kernel version for DigitalOcean
ovs: Update prebuilt kernel version for DigitalOcean

DigitalOcean updated the kernel version in its Ubuntu image.

kayousterhout/quilt,NetSys/quilt,NetSys/quilt,LuiseV/quilt,LuiseV/quilt,ejj/quilt-dev,kklin/quilt,kklin/quilt,quilt/quilt,ejj/quilt-dev,kklin/kelda,NetSys/quilt,kayousterhout/quilt,quilt/quilt,ejj/quilt-dev,kayousterhout/quilt,kklin/quilt,LuiseV/quilt,kelda/kelda,kklin/kelda,kelda/kelda,kelda/kelda,kayousterhout/quilt,NetSys/quilt,LuiseV/quilt,NetSys/quilt,ejj/quilt-dev,kklin/kelda,kklin/kelda,kelda/kelda,quilt/quilt,LuiseV/quilt,kklin/quilt,quilt/quilt