CLOUDSTACK-6317 [VMware] Tagged VLAN support broken for Management/Control/Storage traffic

Check if switch name detected from traffic label for management, storage, control traffic is null before falling back to default value.

Signed-off-by: Sateesh Chodapuneedi <sateesh@apache.org>
CLOUDSTACK-6564: OVS distributed routing: use file based OF rule updates

use ovs-ofctl replace flows by file name option to update the OF rules
instead of sequenetially configuring the rules.