Fix: cannot get default master advertise address correctly
Set default value of NUM_MASTERS and NUM_NODES by MASTERS and NODES themself
Code cleanup and documented
Using runtime reconfiguration for etcd cluster instead of etcd discovery
Add exceptions for verify-flags
Automatic merge from submit-queue
Ubuntu: Enable ssh compression when downloading binaries during cluster creation
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resolves#20971 by using the options provided by ssh.
Native ssh compression has existed for years, and the server is free to disregard the setting, so this should be safe.
With things like the kube binaries I see about a 2x speed increase.
```
λ time scp kubes-bin.tar 9.30.182.251:/mnt/build/kubin
kubes-bin.tar 100% 344MB 10.7MB/s 00:32
real 0m32.284s
user 0m1.679s
sys 0m1.263s
λ time scp -C kubes-bin.tar 9.30.182.251:/mnt/build/kubin
kubes-bin.tar 100% 344MB 22.9MB/s 00:15
real 0m14.810s
user 0m12.858s
sys 0m0.994s
λ ls -lah kubes-bin.tar
-rw-r--r-- 1 mhb staff 344M Jun 2 15:29 kubes-bin.tar
λ tar -tf kubes-bin.tar
kubectl
master/
master/etcd
master/etcdctl
master/flanneld
master/kube-apiserver
master/kube-controller-manager
master/kube-scheduler
node/
node/flanneld
node/kube-proxy
node/kubelet
```
Matthias Bertschy