Comment 3 for bug 1448254

I have a the same problem.
In systemd, there are two files openvswitch-nonetwork.service openvswitch-switch.service which are supposed to fix this problem

I am testing OpenStack with VXLAN and require

sudo ovs-vsctl add-br br-eth2
sudo ovs-vsctl set port br-eth2 tag=2001
sudo ovs-vsctl add-port br-eth2 vxlan1
sudo ovs-vsctl set interface vxlan1 type=vxlan options:remote_ip=192.168.102.205
sudo ovs-vsctl add-port br-eth2 vxlan2
sudo ovs-vsctl set interface vxlan2 type=vxlan options:remote_ip=192.168.102.234
sudo ovs-vsctl add-br br-ex
sudo ovs-vsctl add-port br-ex eth0

then bring up the network from /etc/network/interfaces with

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet manual
    up ifconfig $IFACE 0.0.0.0 up
    up ip link set $IFACE promisc on
    down ip link set $IFACE promisc off
    down ifconfig $IFACE down

auto br-ex
iface br-ex inet static
    address 192.168.102.206
    netmask 255.255.255.0
    gateway 192.168.102.36
    dns-nameservers 192.168.102.10 192.168.102.50
    up ip link set $IFACE promisc on
    down ip link set $IFACE promisc off

auto br-eth2
iface br-eth2 inet static
    address 10.1.0.11
    netmask 255.255.255.0
    up ip link set $IFACE promisc on
    down ip link set $IFACE promisc off
    mtu 1446

from "sudo systemctl list-unit-files" i get

openvswitch-nonetwork.service static
openvswitch-switch.service enabled

so I assume they are running