Fix rooted accounts cleanup, simplify locking (#12194)

Co-authored-by: Carl Lin <carl@solana.com>

runtime/benches/accounts.rs

@@ -137,6 +137,6 @@ fn bench_delete_dependencies(bencher: &mut Bencher) {
         accounts.add_root(i);
     }
     bencher.iter(|| {
-        accounts.accounts_db.clean_accounts();
+        accounts.accounts_db.clean_accounts(None);
     });
 }