HFP: Use disableinbandringing instead of enableinbandringing

* Use disableinbandringing system property as in-band ringing is enabled
  by default so an active user choice would disable it instead of
  enabling it

Bug: 65383086
Test: make, try toggling the preference and verify in-band ringing
      behavior

Change-Id: I9b10743960c933b223481d2efb68af538689c507