Etcd embed auto compaction retention negative value causing a compaction loop or a crash

Summary

### Impact Data Validation ### Detail The parseCompactionRetention function in embed/etcd.go allows the retention variable value to be negative and causes the node to execute the history compaction in a loop, taking more CPU than usual and spamming logs. ### References Find out more on this vulnerability in the [security audit report](https://github.com/etcd-io/etcd/blob/master/security/SECURITY_AUDIT.pdf) ### For more information If you have any questions or comments about this advisory: * Contact the [etcd security committee](https://github.com/etcd-io/etcd/blob/master/security/security-release-process.md#product-security-committee-psc)