supplicant(vts): Stop adding empty instance for vendor HAL am: b9ddf021d3 am: 8a4e68b788 am: 329fe1ca18 am: a8cec5d5ce

Original change: https://android-review.googlesource.com/c/platform/hardware/interfaces/+/1438028

Change-Id: I332a0a820f480104557d9fd69657dcc401b2da0b