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/IptablesBaseTest.cpp b/server/IptablesBaseTest.cpp
index bc56b49..c81773b 100644
--- a/server/IptablesBaseTest.cpp
+++ b/server/IptablesBaseTest.cpp
@@ -68,7 +68,7 @@
 
     std::string realCmd = StringPrintf("echo '%s'", sPopenContents.front().c_str());
     sPopenContents.pop_front();
-    return popen(realCmd.c_str(), "r");
+    return popen(realCmd.c_str(), "r");  // NOLINT(cert-env33-c)
 }
 
 int IptablesBaseTest::fakeExecIptablesRestoreWithOutput(IptablesTarget target,