CallTracker: Add delay to reduce cpu load

A delay is introduced to avoid rapid repeated polling which leads to
high cpu usage and spamming of the modem and logcat.

Change-Id: I6eb12babb723b5f5164ef43493c971f607746484
Merge "CallTracker: Add delay to reduce cpu load" into jb-mr1

Change-Id: I78dd70be1d73b4b7091c309dba771e89611dcfa5