Handle “already authenticated” with authentication race

When the host initiates an authentication but is raced by a
device-initiated authentication and the device-initiated authentication
completes first, the "already authenticated" handling leaves the
host-initiated authentication request in a pending state. For RFCOMM
channels, this results in a pending socket port that does not close
until a timeout occurs, which later can compete with HFP opening.

Bug: 301563951
Tag: #floss
Test: emerge-brya floss
Test: m com.android.btservices

Change-Id: Ib682dbed7032580d83f9921310321ba677668fbf