When image is built without --static-iface option and static
address is set up by cloud-init an interface can have duplicate
stanzas in both /etc/network/interfaces and in
/etc/network/interfaces.d/50-cloud-init. In this case dhclient is
launched for itnerface with static address configured by cloud-init.

This commit introduces --static-iface type=cloud-init option which just
writes loopback config and source /etc/network/interfaces.d/* in
/etc/network/interfaces

    fails because the port is already added in OVS.

    file in /etc/network/interfaces/60-deadline-scheduler-to-all-sdx.rules).

    if we're using bonding (on top of already set "bonding mode=4").