Camera NDK: don't explicit delete ACameraMetadata

To fix the warning in RefBase destructor.

Test: NDK CTS tests, and ARCore measure app.
Bug: 112775599
Change-Id: Ia448ac6d7e6c17699c16d287f65fc2826c9d7578
diff --git a/camera/ndk/NdkCameraMetadata.cpp b/camera/ndk/NdkCameraMetadata.cpp
index 65de81f..34ec2da 100644
--- a/camera/ndk/NdkCameraMetadata.cpp
+++ b/camera/ndk/NdkCameraMetadata.cpp
@@ -57,13 +57,15 @@
         ALOGE("%s: src is null!", __FUNCTION__);
         return nullptr;
     }
-    return new ACameraMetadata(*src);
+    ACameraMetadata* copy = new ACameraMetadata(*src);
+    copy->incStrong((void*) ACameraMetadata_copy);
+    return copy;
 }
 
 EXPORT
 void ACameraMetadata_free(ACameraMetadata* metadata) {
     ATRACE_CALL();
     if (metadata != nullptr) {
-        delete metadata;
+        metadata->decStrong((void*) ACameraMetadata_free);
     }
 }