HFP: Fix headset state transition on device replacement

* When a new HFP device connected to replace the current one, we should
  only send one intent going from CONNECTED to DISCONNECTING
* Change Icb1a7215ff6d9491afbb5f7f203ca0a2c6b7f43a introduces an extra
  intent that broke this flow, resulting in overall state mismatch

Bug: 65591907
Test: Connect to one HFP device and then connect to another HFP device
      the first one is connected

Change-Id: Id0879abbe6924d29a098876d1d312b739a38337a
(cherry picked from commit 6e526638)