Wei Zhou found another statement that was effected by commit 3a999e7 in

OvsVifDriver.isBridgeExists.

Based on commit 725bed43b4 in master

plugins/hypervisors/kvm/src/com/cloud/hypervisor/kvm/resource/OvsVifDriver.java

@@ -165,7 +165,7 @@ public class OvsVifDriver extends VifDriverBase {
         command.add("-c");
         command.add("ovs-vsctl br-exists " + bridgeName);
         String result = command.execute(null);
-        if ("Ok".equals(result)) {
+        if ("0".equals(result)) {
             return true;
         } else {
             return false;