Set owner and administrator UIDs for test networks.

This change sets the owner and administrator UIDs for test networks when
their initial values match the UID for the app creating the test
network. This ensures that apps registering test networks can only make
themselves owners / administrators of the network.

Bug: 153449964
Test: atest NetworkAgentTest
Change-Id: I3a974700aa1d83cb285295ed1de0aa263e2e5b58