update for real location of ip-up-vpn

cheetah:/ # find / 2>/dev/null | egrep '[-]vpn'
/system/bin/ip-up-vpn

Bug: 263463339
Test: TreeHugger
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: If6fd22d1838cfe971be2a87f5ff59a1c6ef65026

main.c

diff --git a/main.c b/main.c
index d33775a..63862c5 100644
--- a/main.c
+++ b/main.c
@@ -118,7 +118,7 @@
         exit(1);
     }
     sprintf(*envp, "INTERFACE=%s", ifr.ifr_name);
-    return "/bin/ip-up-vpn";
+    return "/system/bin/ip-up-vpn";
 }
 
 #endif