Camera: reset callback after test done

Back port from master

Test: VTS test pass
Bug: 63570734
Change-Id: Ic0eecaf843b5c2e78f60325090ea652d43a74a0b
Merged-In: Ic0eecaf843b5c2e78f60325090ea652d43a74a0b
diff --git a/camera/provider/2.4/vts/functional/VtsHalCameraProviderV2_4TargetTest.cpp b/camera/provider/2.4/vts/functional/VtsHalCameraProviderV2_4TargetTest.cpp
index 5ece765..8a1e3df 100644
--- a/camera/provider/2.4/vts/functional/VtsHalCameraProviderV2_4TargetTest.cpp
+++ b/camera/provider/2.4/vts/functional/VtsHalCameraProviderV2_4TargetTest.cpp
@@ -1072,6 +1072,9 @@
     auto status = mProvider->setCallback(cb);
     ASSERT_TRUE(status.isOk());
     ASSERT_EQ(Status::OK, status);
+    status = mProvider->setCallback(nullptr);
+    ASSERT_TRUE(status.isOk());
+    ASSERT_EQ(Status::OK, status);
 }
 
 // Test if ICameraProvider::getCameraDeviceInterface returns Status::OK and non-null device