Streamline conditional stack/btm/btm_ble::btm_ble_connected

Towards readable code

Bug: 163134718
Tag: #refactor
Test: act.py -tc BleCocTest
Test: ble paired 2 phones
Test: classic paired Bose SoundLink

Change-Id: I908ff98f333e173762d25b1e6820db7a433af3af