*   Upgraded to go1.9. ([#51375](https://github.com/kubernetes/kubernetes/pull/51375),[ @cblecker](https://github.com/cblecker))
*   Add-on manager now supports HA masters. ([#55466](https://github.com/kubernetes/kubernetes/pull/55466),[ #55782](https://github.com/x13n),[ @x13n](https://github.com/x13n))

- Fix the bug that EndpointSlice for masters wasn't created after enabling EndpointSlice feature on a pre-existing cluster. ([#84421](https://github.com/kubernetes/kubernetes/pull/84421), [@tnqn](https://github.com/tnqn))

- disableAvailabilitySetNodes is added to avoid VM list for VMSS clusters. It should only be used when vmType is "vmss" and all the nodes (including masters) are VMSS virtual machines. ([#87685](https://github.com/kubernetes/kubernetes/pull/87685), [@feiskyer](https://github.com/feiskyer)) [SIG Cloud Provider]

* Fix scheduler cache panic when updating pod conditions. ([#56733](https://github.com/kubernetes/kubernetes/pull/56733), [@bsalamat](https://github.com/bsalamat))
* Set route_localnet on nodes & masters in GCE ([#55004](https://github.com/kubernetes/kubernetes/pull/55004), [@ihmccreery](https://github.com/ihmccreery))

* When using client or server certificate rotation, the Kubelet will no longer wait until the initial rotation succeeds or fails before starting static pods.  This makes running self-hosted masters with rotation more predictable. ([#58930](https://github.com/kubernetes/kubernetes/pull/58930), [@smarterclayton](https://github.com/smarterclayton))

* **the `gce` provider ensures the bootstrap admin token user is included in the super-user group ([#39537](https://github.com/kubernetes/kubernetes/pull/39537), [@liggitt](https://github.com/liggitt))**
* Remove support for debian masters in GCE kube-up. ([#41666](https://github.com/kubernetes/kubernetes/pull/41666), [@mikedanese](https://github.com/mikedanese))

* Fix session affinity issue with external load balancer traffic when ExternalTrafficPolicy=Local. ([#55519](https://github.com/kubernetes/kubernetes/pull/55519), [@MrHohn](https://github.com/MrHohn))
* Addon manager supports HA masters. ([#55782](https://github.com/kubernetes/kubernetes/pull/55782), [@x13n](https://github.com/x13n))