Disabled gNMI support in p4vm until it becomes more stable

Change-Id: If2085d5824a2b9d06b249bf8d82d92fd384de5af
diff --git a/tools/dev/p4vm/export-ova.sh b/tools/dev/p4vm/export-ova.sh
index 7b94f23..757f94b 100755
--- a/tools/dev/p4vm/export-ova.sh
+++ b/tools/dev/p4vm/export-ova.sh
@@ -15,13 +15,11 @@
     ssh -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no \
     -p ${SSH_PORT} sdn@127.0.0.1 "bash /vagrant/pre-ova-cleanup.sh"
 
-# Wait for VM to power off
-sleep 10
-
-# Make sure VM is not running
-vagrant halt
-
 sleep 5
+vboxmanage controlvm ${VB_UUID} acpipowerbutton
+
+# Wait for VM to power off
+sleep 30
 
 # Remove vagrant shared folder
 vboxmanage sharedfolder remove ${VB_UUID} -name "vagrant"