netd: Enable clang-tidy and fix all warnings

Bug: 65246407
Test: m netd && system/netd/tests/runtests.sh
Change-Id: I1d22b2bc317fe7218ccde78859ed0623d6a1f8df
diff --git a/server/FirewallController.cpp b/server/FirewallController.cpp
index 3d51cb6..6e572af 100644
--- a/server/FirewallController.cpp
+++ b/server/FirewallController.cpp
@@ -247,7 +247,7 @@
     }
 
     std::string command = "*filter\n";
-    for (std::string chainName : chainNames) {
+    for (const std::string& chainName : chainNames) {
         StringAppendF(&command, "%s %s -m owner --uid-owner %d -j %s\n",
                       op, chainName.c_str(), uid, target);
     }