Partially populate WifiUsabilityStatsEntry even without vendor HAL

Some devices do not have a vendor HAL, in particular the
Android Virtual Device used for testing. So fill in the fields
that we can, so that the API can be tested on these devices.

Bug: 152910948
Test: atest android.net.wifi.cts.ConnectedNetworkScorerTest
Change-Id: I91a70e4f7f58020667969bc2e68ae1d7f85bdd99
1 file changed