Keystore 2.0: Implement onDeviceOffBody.

Add onDeviceOffBody to KeystoreMaintenance interface.

Also rename user_namanger.rs to maintenance.rs.

Bug: 171305684
Test: N/A
Change-Id: I382213533c3891084159cefce8c32b4fe69e91bc
diff --git a/keystore2/src/keystore2_main.rs b/keystore2/src/keystore2_main.rs
index 1ce3e14..09ffecb 100644
--- a/keystore2/src/keystore2_main.rs
+++ b/keystore2/src/keystore2_main.rs
@@ -17,9 +17,9 @@
 use keystore2::authorization::AuthorizationManager;
 use keystore2::entropy;
 use keystore2::globals::ENFORCEMENTS;
+use keystore2::maintenance::Maintenance;
 use keystore2::remote_provisioning::RemoteProvisioningService;
 use keystore2::service::KeystoreService;
-use keystore2::user_manager::Maintenance;
 use keystore2::{apc::ApcManager, shared_secret_negotiation};
 use log::{error, info};
 use std::{panic, path::Path, sync::mpsc::channel};