HFP: Reset BTA SCO control block when bta_ag_create_sco failed

* When trying to connect SCO to non-active and active device back to
  back, the first connection to non-active device must fail gracefully
* Otherwise, BTA SCO state machine may stuck in a irrecoverable state
* Schedule to send AUDIO_CONNECTING state before starting SCO connection
  to avoid race condition between connecting state and connection
  failure

Bug: 111101075
Test: Manual test, make a call and switch path A->speaker->B on phone UI
Change-Id: I9bfa389e04863944d88f2bca49d27f1247fa072b