Fix jarjar rule for LocalLog

LocalLog is in android.util, not android.net.
The previous code used to work because methods used by NetworkStack are
@UnsupportedAppUsage, but this should be avoided because the symbols are
not stable.

Bug: 160113128
Test: m; atest NetworkStackTests; manual: wifi working
(cherry-pick from AOSP with conflicts)
Merged-In: I3864ce089c02d53dfc6d0f9c58ac4a84daaaf787

Change-Id: I3864ce089c02d53dfc6d0f9c58ac4a84daaaf787