BTA HF_CLIENT: Always reply to +BCS

Phones don't like when we don't reply to +BCS codec-negotiation. We were
having this behavior because not always do we want to accept a
connection request over SCO. Instead of not replying to +BCS (which is
essentially a codec negotiation) we rather refuse the SCO request when
it comes in. This creates other issues such as some phones trying to
connect SCO in an infinite loop but it still keeps interoperability with
other devices such as iPhones and Microsoft phones intact

Bug: b/35469963
Bug: b/35431871
Bug: b/35419773

Test: SCO (Phone Audio) test with iPhone, Microsoft and Nexus phones

Change-Id: I5319edcb4da9d66c6d6b3a49742248c90dee98e6