[Bugfix] Don't delete mPendingUids if PendingTopPid is added later than updateOomAdj started

Analysis:
1.Doing updateOomAdjInnerLSP in backgroud, and it would last for a long
time
2.Now start a new Activity, windowManager save the latest topUid into PendingStartActivityUids
3.updateOomAdj task in step.1 done, and then delete all uids in PendingStartActivityUids
4.The topApp will be rejected by AppOps due to the deleting in step.3

Signed-off-by: huang chaopeng <huangchaopeng@oppo.corp-partner.google.com>
Change-Id: I52c7c2a8d6cb86b27b1f008cb56f670ce7698dc9