Fix netId testing on Q and R

Do not call getNetId() on Q as it did not exist yet. Add a separate test
for getNetId(), only run after Q.

Also add testing for getNetIdForResolv and fromNetworkHandle on Q and R.

Bug: 185731396
Test: atest NetworkTest
Change-Id: I03f9eb0c94b09dc285018e9887fe20d95a93ae45