net_test_btif: Properly call btif_dm_cleanup in tear down am: 6cea879f am: 817574ad

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Bluetooth/+/3047616



Change-Id: Ic71755db0870d467a9486ee3d6d6891a03773b93
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>