proxmox-backup-proxy: fix leftover references on datastore removal

when we remove a datastore via api/cli, the proxy
has sometimes leftover references to that datastore in its
DATASTORE_MAP which includes an open filehandle on the
'.lock' file

this prevents unmounting/exporting the datastore even after removal,
only a reload/restart of the proxy did help

add a command to our command socket, which removes all non
configured datastores from the map, dropping the open filehandle

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
Signed-off-by: Dietmar Maurer <dietmar@proxmox.com>

src/bin/proxmox-backup-proxy.rs

@@ -136,6 +136,17 @@ async fn run() -> Result<(), Error> {
         },
     )?;
 
+    // to remove references for not configured datastores
+    commando_sock.register_command(
+        "datastore-removed".to_string(),
+        |_value| {
+            if let Err(err) = proxmox_backup::backup::DataStore::remove_unused_datastores() {
+                log::error!("could not refresh datastores: {}", err);
+            }
+            Ok(Value::Null)
+        }
+    )?;
+
     let server = daemon::create_daemon(
         ([0,0,0,0,0,0,0,0], 8007).into(),
         move |listener, ready| {