Let netd decide when to swap stats map

To protect stats map from overflow, netd need to know how many stats
entries exist in the current live stats map when tagging the socket. To
prevent racing against framework stats reading actions during tagging
sockets, let netd handle the map swap action instead.

Bug: 111441138
Test: android.app.usage.cts.NetworkUsageStatsTest
      android.net.cts.TrafficStatsTest

Change-Id: I1b63e50a67be07472dba32744c8598c1788d0b75