Release wakelock for incoming SMS

- In the current implementation, a wakelock is
acquired when SMS is received in IdleState. The
wakelock is released only 3 seconds after returning
back to IdleState. As the statemachine will be back
in IdleState only after SMS processing is complete,
there is no need to hold the wakelock for another
3 seconds

- Add a change to hold wakelock for 3 seconds as a
worst case timeout rather than for normal processing
of SMS. Also maintain a wakelock counter to make sure
that wakelock is released when statemachine is idle

Change-Id: I826603d7e5d8ea5ced3d331ddb17618be0390ffe
CRs-Fixed: 875160