Add basic logging infrastructure for bugreports

Test: as follows
    - built, flashed, booted
    - "adb shell dumpsys netd" shows logs
    - tests/runtests.sh passes
Change-Id: I0e44da7f9a9cc53074ffc396b958e9e2dbcd2603
diff --git a/server/NetworkController.cpp b/server/NetworkController.cpp
index 5bbfe3f..ed5156f 100644
--- a/server/NetworkController.cpp
+++ b/server/NetworkController.cpp
@@ -690,7 +690,7 @@
     dw.incIndent();
     for (const auto& i : mNetworks) {
         Network* network = i.second;
-        dw.println(network->toString().c_str());
+        dw.println(network->toString());
         if (network->getType() == Network::PHYSICAL) {
             dw.incIndent();
             Permission permission = reinterpret_cast<PhysicalNetwork*>(network)->getPermission();