CLOUDSTACK-4443 [VMWARE]Failed to deploy VM's on VMWARE Standard vSwitch Legacy Zone after upgrade

While upgrading to 4.2 to support existing clusters working over standard vswitch or nexus dvswitch should be supported as is. To ensure this while upgrading to 4.2, existing cluster's vswitch configuration needs to be persisted to database. If zone level traffic label is empty then default vswitch name would be used.

Signed-off-by: Sateesh Chodapuneedi <sateesh@apache.org>