Support unlabeled vsock sockets for adbd.

The connections that come in from the host are currently unlabeled.

Bug: 130376148
Change-Id: I087b36f50375d91f6e2de87b77795c24181b21ba
Test: Ran on GCE
(cherry picked from commit d0b151e97e2a6a09e38293c7c620463e60a6ce5d)