[4/7] Remove code for removing old kernel
[4/7] Remove code for removing old kernel

After updating the kernel, Bionic does no longer allow the removal of
the running kernel the way Xenial did.

This changeset deletes the removal code. We keep the old kernel, which
results in a slightly larger basedisk.

Change-Id: I48117238ac852ad86e6a15cd3d46578243ac3d3c

openstack/training-labs,openstack/training-labs,openstack/training-labs