Replace RW lock with mutex, shared_mutex

Test: built, flashed, booted
      system/netd/tests/runtests.sh passes
Change-Id: I42b52d815b6ba0ba6f93dc27e83a900d2abec715
diff --git a/server/RouteController.h b/server/RouteController.h
index 6e10cce..57920d6 100644
--- a/server/RouteController.h
+++ b/server/RouteController.h
@@ -20,9 +20,10 @@
 #include "NetdConstants.h"
 #include "Permission.h"
 
-#include <map>
-#include <sys/types.h>
 #include <linux/netlink.h>
+#include <sys/types.h>
+#include <map>
+#include <shared_mutex>
 
 namespace android {
 namespace net {
@@ -110,9 +111,8 @@
 
 private:
     friend class RouteControllerTest;
-
     // Protects access to interfaceToTable.
-    static android::RWLock sInterfaceToTableLock;
+    static std::shared_mutex sInterfaceToTableLock;
     static std::map<std::string, uint32_t> sInterfaceToTable;
 
     static int configureDummyNetwork();