CLOUDSTACK-6832: [OVS]vnet is not released even the network is deleted

fix ensures allocated VNET is released during network shutdown

(cherry picked from commit be937a08213f06a801cf07d19867d48dad35d19f)
CLOUDSTACK-6749: [OVS] xe network-param-get with
param-key=is-ovs-vpc-distributed-vr-network alway returns error

fixing unnecessary errors in the logs

(cherry picked from commit 9dfbdb5ffd2f0981651bc98f1c5d71718a24a29f)