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 branch 'cm-10.1' of github.com:CyanogenMod/android_frameworks_opt_telephony into cm-10.1