Fix ndc network create vpn command

Create vpn from ndc is broken since aosp/841619. Correct argc number to
make it work.

Test: adb shell ndc network create 150 vpn 0
Change-Id: I4e8f9480b9159409bbcf53bd25bef5a3f699584c
diff --git a/server/NdcDispatcher.cpp b/server/NdcDispatcher.cpp
index ad3dc37..e5cad45 100644
--- a/server/NdcDispatcher.cpp
+++ b/server/NdcDispatcher.cpp
@@ -1049,7 +1049,7 @@
             return syntaxError(cli, "Missing argument");
         }
         unsigned netId = stringToNetId(argv[2]);
-        if (argc == 6 && !strcmp(argv[3], "vpn")) {
+        if (argc == 5 && !strcmp(argv[3], "vpn")) {
             bool secure = strtol(argv[4], nullptr, 2);
             if (Status status = mNetd->networkCreateVpn(netId, secure); !status.isOk()) {
                 return operationError(cli, "createVirtualNetwork() failed",