Telephony: Do not display the data icon if data is not connected.

When updating the status bar for the bluetooth reverse tether
connected status, even if the mobile data state is in
disconnected state, and it shows the data icon based on the
data network type.
Changes made to check the mobile data connected condition while
updating the data icon.

Change-Id: Iabd6269cc23c1e0ebd5fc140fc14c9ec67883148
CRs-Fixed: 356684