Remove BootControlInterface::Cleanup

It is just a wrapper around GetDynamicPartitionControl()->Cleanup().
Delete it and let callers call it instead.

Test: update_engine_unittests

Change-Id: I068228a43dac122828c28bbc49a0f6f77e5b6ff2
diff --git a/update_attempter_android.cc b/update_attempter_android.cc
index 5bffc42..b76e05b 100644
--- a/update_attempter_android.cc
+++ b/update_attempter_android.cc
@@ -597,7 +597,7 @@
     return;
   }
 
-  boot_control_->Cleanup();
+  boot_control_->GetDynamicPartitionControl()->Cleanup();
 
   download_progress_ = 0;
   UpdateStatus new_status =