switch from failure to anyhow

Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>

src/bin/proxmox-backup-proxy.rs

@@ -1,6 +1,6 @@
 use std::sync::Arc;
 
-use failure::*;
+use anyhow::{bail, format_err, Error};
 use futures::*;
 use hyper;
 use openssl::ssl::{SslMethod, SslAcceptor, SslFiletype};