api: datastore: add missing log context for prune

Adds the missing log context for cases were a prune is not executed as
dedicated tokio task.

Commit 432de66a ("api: make prune-group a real workertask") moved the
prune group logic into it's own tokio task conditionally.

However, the log context was missing for cases where no dedicated
task/thread is started, leading to the worker task state being
unknown after finish, as no logs are written to the worker task log
file.

Reported in the community forum:
https://forum.proxmox.com/threads/161273/

Signed-off-by: Christian Ebner <c.ebner@proxmox.com>
Reviewed-by: Gabriel Goller <g.goller@proxmox.com

src/api2/admin/datastore.rs

@@ -19,6 +19,7 @@ use tracing::{info, warn};
 use proxmox_async::blocking::WrappedReaderStream;
 use proxmox_async::{io::AsyncChannelWriter, stream::AsyncReaderStream};
 use proxmox_compression::zstd::ZstdEncoder;
+use proxmox_log::LogContext;
 use proxmox_router::{
     http_err, list_subdirs_api_method, ApiHandler, ApiMethod, ApiResponseFuture, Permission,
     Router, RpcEnvironment, RpcEnvironmentType, SubdirMap,
@@ -1112,9 +1113,13 @@ pub fn prune(
         )?;
         Ok(json!(upid))
     } else {
-        let (worker, _) = WorkerTask::new("prune", Some(worker_id), auth_id.to_string(), true)?;
+        let (worker, logger) =
+            WorkerTask::new("prune", Some(worker_id), auth_id.to_string(), true)?;
+        let result = LogContext::new(logger).sync_scope(|| {
             let result = prune_group(worker.clone());
             worker.log_result(&Ok(()));
+            result
+        });
         Ok(json!(result))
     }
 }