add some VCPU for mirror image

Change-Id: I806d55c6024c6dd6fae0cfd9651dd48042280bac
diff --git a/mirror-image/template.json b/mirror-image/template.json
index f7e668b..711f7ed 100644
--- a/mirror-image/template.json
+++ b/mirror-image/template.json
@@ -138,7 +138,7 @@
         ],
         [
           "-smp",
-          "4"
+          "8"
         ],
         ["-device", "virtio-net,netdev=user.0"],
         ["-object","rng-random,id=objrng0,filename=/dev/urandom"],