Enabled TLS encrypted communication for etcd

[klention]

Issue: #822

Related PR: #849

TLS Communication Encryption is now enabled for:

• Between PostgreSQL nodes
• Between PgBouncer and PostgreSQL nodes
• Between etcd nodes
• Between Patroni and etcd nodes
• Between vip-manager and etcd nodes
• Between confd and etcd nodes

[klention]

Resolves #822

[klention]

#859

[vitabaks]

Great job @klention! Thanks a lot for the contribution.

The remaining task is to implement TLS between the confd service and etcd nodes to ensure full TLS coverage across all cluster components (not considering the consul cluster).

Configuration options:

• client_cakeys (string) - The client CA key file.
• client_cert (string) - The client cert file.
• client_key (string) - The client key file.

Doc: https://github.com/kelseyhightower/confd/blob/master/docs/configuration-guide.md

UPD: I'll do it.

[klention]

Great job @klention! Thanks a lot for the contribution.

The remaining task is to implement TLS between the confd service and etcd nodes to ensure full TLS coverage across all cluster components (not considering the consul cluster).

Configuration options:

• client_cakeys (string) - The client CA key file.
• client_cert (string) - The client cert file.
• client_key (string) - The client key file.

Doc: https://github.com/kelseyhightower/confd/blob/master/docs/configuration-guide.md

UPD: I'll do it.

Thank you for all of this 👍