Revert "NetworkStatsService: Fix getDetailedUidStats to take VPNs into account."

This reverts commit 29d2ef2f.

Reason for revert: This change has been implicated in 4-way deadlocks as seen in b/134244752.

Bug: 134244752
Change-Id: I37f75c2b243ea548a88ef1dae88287405c6ef55f
Merged-In: I0c00e8f0e30cee987b71b561079a97bf09d4dae4