Linux bridges are automatically set UP when
any parent interface is UP.

But for OVS bridges it doesn't work.

For dpdk and non-dpdk bridges, always create a
config file in /etc/network/interfaces.u/ and
bring the bridge interface up after it is configured,
even if it doesn't have IP address.

Change-Id: I92888ce0d373e412dfb7ed2e2398c0d4d008e301
Closes-Bug: https://mirantis.jira.com/browse/PROD-24343