fix/complete k8s 1.27.10 upgrade

I've just found out that one critical bit of !1753 (merged) was missing, resulting in us still deploying 1.27.6 by default, although with OS images only having k8s 1.27.10 pre-downloaded... 😬

Note that we had downstream CI testing that was done on main in the meantime, where k8s_version was force-set to 1.27.10+rke1, so for RKE2 I don't expect this MR to give us surprising CI results.