update_engine: Remove release/aquire semantic from scoped_ptr/unique_ptr

Now that scoped_ptr is just a type alias to unique_ptr, there is no
longer a need to convert between the two by using .release() and
constructing the other with a raw pointer.

BUG: None
TEST: Built for dragonboard, all unit tests pass (except for update_engine,
      but those tests failed before these changes too).

Change-Id: I0afcbc4d85b7ca78149fb29c188d7bcc99d4c80b
diff --git a/boot_control_android.cc b/boot_control_android.cc
index e4d3c16..78df37f 100644
--- a/boot_control_android.cc
+++ b/boot_control_android.cc
@@ -60,7 +60,7 @@
   if (!boot_control->Init()) {
     return nullptr;
   }
-  return brillo::make_unique_ptr(boot_control.release());
+  return std::move(boot_control);
 }
 
 }  // namespace boot_control
diff --git a/boot_control_chromeos.cc b/boot_control_chromeos.cc
index 547e72b..e9ad698 100644
--- a/boot_control_chromeos.cc
+++ b/boot_control_chromeos.cc
@@ -81,7 +81,7 @@
   if (!boot_control_chromeos->Init()) {
     LOG(ERROR) << "Ignoring BootControlChromeOS failure. We won't run updates.";
   }
-  return brillo::make_unique_ptr(boot_control_chromeos.release());
+  return std::move(boot_control_chromeos);
 }
 
 }  // namespace boot_control
diff --git a/common/subprocess.cc b/common/subprocess.cc
index 9738b1d..53cccff 100644
--- a/common/subprocess.cc
+++ b/common/subprocess.cc
@@ -204,7 +204,7 @@
       true,
       base::Bind(&Subprocess::OnStdoutReady, record.get()));
 
-  subprocess_records_[pid].reset(record.release());
+  subprocess_records_[pid] = std::move(record);
   return pid;
 }
 
diff --git a/update_manager/evaluation_context.cc b/update_manager/evaluation_context.cc
index 03ac0b7..63f7d9b 100644
--- a/update_manager/evaluation_context.cc
+++ b/update_manager/evaluation_context.cc
@@ -92,7 +92,7 @@
   MessageLoop::current()->CancelTask(timeout_event_);
   timeout_event_ = MessageLoop::kTaskIdNull;
 
-  return unique_ptr<Closure>(callback_.release());
+  return std::move(callback_);
 }
 
 TimeDelta EvaluationContext::RemainingTime(Time monotonic_deadline) const {