btif: hf: minor refractory of connection state emission

Emit (dis)connecting in the btif_hf layer before the profile is
actually (dis)connected to have a complete session consisting of the
attempt and the result. Improve the comment to provide a little more
context.

BUG: 240781725
Tag: #floss
Test: ./build.py
Test: emerge-${BOARD} floss
Test: gd/cert/run

Change-Id: I8d48194727fb927eb78fba6ffb2c3aa2ab14b81c