Switch previous and new code path in setChildChain

setChildChain was updated to use Java BpfMap class instead of native JNI
functions in aosp/2131752.
But it is better to verify this refactoring by the experiment.
So this commit update setChildChain to switch previous code path(JNI)
and new code path(Java) based on the flag.

Bug: 217624062
Test: atest BpfNetMapsTest android.net.cts.ConnectivityManagerTest#testFirewallBlocking
Change-Id: I47a5e7f631bb6806716f464df26ec2eca46503b3
1 file changed