Cleanup log in MultiNetworkConnectivityTestActivity

It's a follow up of aosp/1666827. Log does not need these
.getNetId calls as they're actually added to a string. Just
use network since the id information is in the toString.

Bug: 182859030
Test: make CtsVerifier
Change-Id: Id144779c6c635fb0423d48e9b9f233fded2cd1f0
1 file changed