Don't assert on AVDTP reference count bugs

In the case that the AVDTP session references weren't fully dropped when a
disconnection happens, in later reconnections the disconnect_timeout
function cound have a reference count higher than 1. These bugs naturally
need to fixed (and there's a proper error() call to log them) but we can
still handle the situation semi-cleanly instead of asserting and aborting
since the AVDTP session struct will just silently hang around and get
reused at the next connection attempt.
1 file changed