Log the time it takes netd to start up.

Currently on, bullhead-eng, I see:

01-21 14:59:26.174 21421 21421 I Netd    : Netd started in 2432ms

Test: restarted netd and observed log message.
Bug: 32323979
Bug: 33279878
Change-Id: I7195d06d7ed1a09858185555f60b07e5bfe306ed
diff --git a/server/main.cpp b/server/main.cpp
index ae3a71a..aab15d6 100644
--- a/server/main.cpp
+++ b/server/main.cpp
@@ -18,6 +18,7 @@
 #include <stdlib.h>
 #include <signal.h>
 #include <errno.h>
+#include <math.h>
 #include <string.h>
 #include <sys/stat.h>
 #include <sys/types.h>
@@ -40,6 +41,7 @@
 #include "NetdConstants.h"
 #include "NetdNativeService.h"
 #include "NetlinkManager.h"
+#include "Stopwatch.h"
 #include "DnsProxyListener.h"
 #include "MDnsSdListener.h"
 #include "FwmarkServer.h"
@@ -63,6 +65,7 @@
 
 int main() {
     using android::net::gCtls;
+    Stopwatch s;
 
     ALOGI("Netd 1.0 starting");
     remove_pid_file();
@@ -122,6 +125,8 @@
 
     write_pid_file();
 
+    ALOGI("Netd started in %dms", static_cast<int>(s.timeTaken()));
+
     IPCThreadState::self()->joinThreadPool();
 
     ALOGI("Netd exiting");