Fixed audioserver crash in monkey test

Enable log function in ToneGenerator.cpp, then ToneGenerator
plays consecutively many times and do not stopTone.

"lpToneGen->mNextSegSmp*1000" will go beyond the scope of unsigned
int, and audioserver get crashed.

Test: Enable log function in ToneGenerator.cpp, alarm notification is
played when the phone is online. ToneGenerator plays consecutively.
Do not stopTone. then we get audioserver crash.

Change-Id: I073590088fccb32a73353d14970dc89441045663