move worker_task.rs into proxmox-rest-server crate

Also moved pbs-datastore/src/task.rs to pbs-tools, which now depends on 'log'.

src/bin/proxmox-backup-manager.rs

@@ -14,9 +14,10 @@ use pbs_api_types::{
     IGNORE_VERIFIED_BACKUPS_SCHEMA, VERIFICATION_OUTDATED_AFTER_SCHEMA,
 };
 
+use proxmox_rest_server::wait_for_local_worker;
+
 use proxmox_backup::config;
 use proxmox_backup::api2;
-use proxmox_backup::server::wait_for_local_worker;
 
 mod proxmox_backup_manager;
 use proxmox_backup_manager::*;