Use end timestamp set in the future to query NetworkStats since boot

This is necessary to include the full active bucket in the stats.
When computing active bucket stats, NetworkStats multiplies data
by (end - activeBucketStart) / (now - activeBucketStart). This is
done in NetworkStatsHistory#getValues which is called from
NetworkStatsCollection#getSummary. In this formula end=min(endTime,
now), where endTime is passed from StatsPullAtomService and now is
the timestamp obtained later in NetworkStatsCollection#getSummary.
This calculation takes place after reading stats.

Test: manual
Bug: 350037915
Flag: EXEMPT bugfix
Change-Id: I161d321aa71eb49459acbe263e087e30f815378b