Fix redundant router switch back to single router

The existed redundant router network didn't change.

server/src/com/cloud/network/router/VirtualNetworkApplianceManagerImpl.java

@@ -875,7 +875,8 @@ public class VirtualNetworkApplianceManagerImpl implements VirtualNetworkApplian
                 }
             }
 
-            if (routers.size() == routerCount) {
+            /* If old network is redundant but new is single router, then routers.size() = 2 but routerCount = 1 */
+            if (routers.size() >= routerCount) {
                 return routers;
             }