HFP: Limiting the mStartcount to 1 for each mScoClient

Some of the VOIP applications call startBluetoothSco()
multiple times. This inturn increments the mStartcount
for each mScoClient. But while the call is terminated,
VOIP applications call stopBluetoothSco() only once.
this results in SCO being still present.

To avoid this issue, the mStartcount value is limited
to 1 even if the application calls startBluetoothSco()
multiple times. Also when the mStartcount reaches 1,
it calls setBluetoothScoOn(true) from the system
context for correct SCO device selection.

Adding logs in some of APIs in files AudioManager
and AudioService for more clarity and analysis
purpose.

CRs-Fixed: 2197250
Change-Id: I2ac759db91087710ac98b27a702059ce8dd0cb1d