fix initial "hfp-enable" state of HFP client state machine.

this is tested on pi-dev in go/ag/4165726

initial state of "hfp-enable" is true.
when a call is placed, since the state is assumed to be
audio-routing already, no effort is made to actually route the audio to HU.

by fixing the initial state to "hfp-enable = false",
tihs problem is circumvented.

Bug: 79857325
Test: tested manually.
Change-Id: I11aa0dadc74db972614a6679c6dcd00fb4b7a291