remove proxmox-protocol subcrate

AFAICT we have no use for it anymore, its api entry points
are gone. If we do end up needing something from it, it's
still in the git history anyway. (And about two thirds of it
can be made much less awkward by utilizing async-await
anyway, so no love lost there...)

Moved the chunker back into src/backup/chunker.rs

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

src/backup/chunk_stream.rs

@@ -1,10 +1,9 @@
-use failure::*;
-
-use proxmox_protocol::Chunker;
-use futures::{Async, Poll};
-use futures::stream::Stream;
-
 use bytes::BytesMut;
+use failure::*;
+use futures::stream::Stream;
+use futures::{Async, Poll};
+
+use super::Chunker;
 
 /// Split input stream into dynamic sized chunks
 pub struct ChunkStream<S> {