Add static lock in PowerProfile

Before this cl, there exists nullpointer crash in PowerProfile in
following part:

"sPowerMap.containsKey(key) && (Double) sPowerMap.get(key) > 0"

To my best knowledge, it is because in
PowerUsageSummary.SummaryProvider, we may create batterystats in
meantime:
1. setListening is invoked in worker thread, in which we will force
update the batterystats.
2. In setListening we will register receiver, which may update
batterystats through onReceive in UI thread.

This cl adds static lock in PowerProfile, making the init part can
only be accessed by an thread at a time.

Bug: 64209576
Test: Manual
Change-Id: I00bc094f44416669b4f0e11e647b0fae2ff61013