Replace .kill() with .terminate() to terminate subprocesses

tunnel.py

@@ -121,7 +121,7 @@ class TunnelManager:
         utils.log('Killing the connection with %s...' % (prefix,), 2)
         connection = self._connection_dict.pop(prefix)
         try:
-            connection.process.kill()
+            connection.process.terminate()
         except OSError:
             # If the process is already exited
             pass

vifibnet.py

@@ -165,22 +165,22 @@ def main():
                 forwarder.refresh()
     except KeyboardInterrupt:
         try:
-            router.kill()
+            router.terminate()
         except:
             pass
         try:
-            server_process.kill()
+            server_process.terminate()
         except:
             pass
         tunnel_manager.killAll()
         return 0
     except:
         try:
-            router.kill()
+            router.terminate()
         except:
             pass
         try:
-            server_process.kill()
+            server_process.terminate()
         except:
             pass
         try: