- getCluster: now deduplicates the node list (i.e. overwrites existing
nodes in the list with "fresh" nodes and appends new ones)
- UpdateLoadbalancerConfig: print warning if "host not found in
upstream" returned by nginx after updating the config, as it's not a
failure per se, but shouldn't be ignored
- use idempotent UpdateKubeconfig which takes a fresh list of master
nodes and uses it to update the loadbalancer
- removeNode: use aforementioned function to update the loadbalancer
config when removing a master node
- package cluster: use context.Context as first function param in every
exported function
- package cmd: pass cmd.Context() to calls to package cluster exported
functions
