DO NOT MERGE: Fix setTorchMode support for the old HAL version

CameraHardwareInterfaceFlashControl class calls disconnectCameraDevice
when torch is disabled. This closes connection to the camera module,
but mDevice instance is kept and variable is non-NULL which will
prevent connection next time torch is going to be enabled.

Bug: 24909924
Change-Id: Icb1ffb07f05256afd92821f0f4908cda5332c05b
diff --git a/services/camera/libcameraservice/CameraFlashlight.cpp b/services/camera/libcameraservice/CameraFlashlight.cpp
index 280bb9d..e42c596 100644
--- a/services/camera/libcameraservice/CameraFlashlight.cpp
+++ b/services/camera/libcameraservice/CameraFlashlight.cpp
@@ -878,6 +878,7 @@
     }
     mDevice->setPreviewWindow(NULL);
     mDevice->release();
+    mDevice = NULL;
 
     return OK;
 }