Fix warnings in preparation for Rust 1.54.0

This CL fixes several new warnings generated by rustc 1.54.0.

Bug: 194812675
Test: m rust
Change-Id: I3076313ea51c6f4e74029ad9fb45d6f0b6dea460
diff --git a/keystore2/src/maintenance.rs b/keystore2/src/maintenance.rs
index 9abc5aa..08fa8d2 100644
--- a/keystore2/src/maintenance.rs
+++ b/keystore2/src/maintenance.rs
@@ -206,9 +206,9 @@
             let key_id_guard = match source.domain {
                 Domain::APP | Domain::SELINUX | Domain::KEY_ID => {
                     let (key_id_guard, _) = LEGACY_MIGRATOR
-                        .with_try_migrate(&source, caller_uid, || {
+                        .with_try_migrate(source, caller_uid, || {
                             db.borrow_mut().load_key_entry(
-                                &source,
+                                source,
                                 KeyType::Client,
                                 KeyEntryLoadBits::NONE,
                                 caller_uid,