frameworks/base: move the traces file to avoid data loss.

If an ANR comes just after the framework reboot, the traces for
the framework reboot will get over-written with the ANR traces.
So, We are missing the traces for the framework reboot which
makes debugging the framework reboot difficult.

This patch will rename and will append a unique timestamp
this trace file name for the framework reboot once the
ActivityManager collects the traces. In case of multiple
Watchdog Kills the trace file generated will have diffrent
timestamp so that it does not get overwritten on multiple
Watchdog kills.

Change-Id: I90cb400d06aa909c1560328de4751aa02dbb6858