Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

Update default etcd server to 3.2 for kubernetes 1.11

Repply #59836 but with latest etcd 3.2 patch version (3.2.18 which includes mvcc fix and leader election timeout fix) and default `--snapshot-count` to 10k to resolve performance regression in previous etcd 3.2 server upgrade attempt (https://github.com/kubernetes/kubernetes/issues/60589#issuecomment-372458578).

See https://github.com/kubernetes/kubernetes/issues/60589#issuecomment-372458578 for details on the root cause of the performance regression and scalability test results of setting `--snapshot-count` to 10k.

```release-note
Upgrade the default etcd server version to 3.2.18
```
@gyuho @shyamjvs @jdumars @timothysc