[Bug 1852221] [NEW] ovs-vswitchd needs to be forced to reconfigure after adding protocols to bridges

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[Impact]
When the neutron native ovs driver creates bridges it will sometimes apply/modify the supported openflow protocols on that bridge. The OpenVswitch versions shipped with Train and Ussuri don't support this which results in OF protocol mismatches when neutron performs operations on that bridge. The patch we are backporting here ensures that all protocol versions are set on the bridge at the point on create/init.

[Test Case]
 * deploy Openstack Train
 * go to a compute host and do: sudo ovs-ofctl -O OpenFlow14 dump-flows br-int
 * ensure you do not see "negotiation failed" errors

[Regression Potential]
 * this patch is ensuring that newly created Neutron ovs bridges have OpenFlow 1.0, 1.3 and 1.4 set on them. Neutron already supports these so is not expected to have any change in behaviour. The patch will not impact bridges that already exist (so will not fix them either if they are affected).

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As part of programming OpenvSwitch, Neutron will add to which protocols
bridges support [0].

However, the Open vSwitch `ovs-vswitchd` process does not appear to
always update its perspective of which protocol versions it should
support for bridges:

# ovs-ofctl -O OpenFlow14 dump-flows br-int
2019-11-12T12:52:56Z|00001|vconn|WARN|unix:/var/run/openvswitch/br-int.mgmt: version negotiation failed (we support version 0x05, peer supports version 0x01)
ovs-ofctl: br-int: failed to connect to socket (Broken pipe)

# systemctl restart ovsdb-server
# ovs-ofctl -O OpenFlow14 dump-flows br-int
 cookie=0x84ead4b79da3289a, duration=1.576s, table=0, n_packets=0, n_bytes=0, priority=65535,vlan_tci=0x0fff/0x1fff actions=drop
 cookie=0x84ead4b79da3289a, duration=1.352s, table=0, n_packets=0, n_bytes=0, priority=5,in_port="int-br-ex",dl_dst=fa:16:3f:69:2e:c6 actions=goto_table:4
...
(Success)

The restart of the `ovsdb-server` process above will make `ovs-vswitchd`
reassess its configuration.

0:
https://github.com/openstack/neutron/blob/0fa7e74ebb386b178d36ae684ff04f03bdd6cb0d/neutron/agent/common/ovs_lib.py#L281

** Affects: charm-neutron-openvswitch
     Importance: Undecided
         Status: Invalid

** Affects: cloud-archive
     Importance: Undecided
         Status: Fix Released

** Affects: cloud-archive/train
     Importance: Undecided
         Status: New

** Affects: cloud-archive/ussuri
     Importance: Undecided
         Status: Fix Released

** Affects: kolla-ansible
     Importance: Undecided
         Status: New

** Affects: neutron
     Importance: Undecided
         Status: New

** Affects: openvswitch
     Importance: Undecided
         Status: New

** Affects: openvswitch (Ubuntu)
     Importance: Undecided
         Status: Confirmed

** Affects: openvswitch (Ubuntu Eoan)
     Importance: Undecided
         Status: New

** Affects: openvswitch (Ubuntu Focal)
     Importance: Undecided
         Status: Fix Released


** Tags: patch
-- 
ovs-vswitchd needs to be forced to reconfigure after adding protocols to bridges
https://bugs.launchpad.net/bugs/1852221
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