BT: Send proper updates to headset for call swap

Use case:
1. Connect BT headset.
2. Make MO/MT call.
3. Make another MO/MT call.
4. When one call is active, another is on hold, swap calls from headset.
5. Check call held indicators sent to headset.

Failure:
1. Calls swapped and CIEV 7,2 and CIEV 7,1 is sent on GSM network.
2. For CDMA, calls swapped with in active CDMA conference but no held
call indicator is sent.

Root cause:
1. In gsm network, when active and held calls are swapped, firstly
active call is put to hold making held call count as 2 and
BluetoothPhoneService updates callheld indicator as no call active.
After this, next update comes to make original held call as active
and again callheld indicator as active and held is updated.

2. For CDMA, when calls are swapped, no call held indicator is sent
from Telephony.

Fix:
1. In gsm network, avoid unnecessary callheld indicator update as CIEV7,2
for call swapping.

2. In cdma network, send callheld indicator for call swap within
active conference.

Change-Id: I385e9b383c5c71cab2bf300669695d2fa66bd38c