add generic either-or AsyncRead/Write type

The HttpsConnector will use this. Instead of implementing a
specialized MaybeTlsStream, this is simply a generic "either
this or that kind of Async Read/Write type".

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

src/tools.rs

@@ -16,6 +16,7 @@ use serde_json::Value;
 use proxmox::tools::vec;
 
 pub mod acl;
+pub mod async_io;
 pub mod async_mutex;
 pub mod borrow;
 pub mod daemon;