[SRU] openvswitch 2.12.3

[Impact]

This release sports mostly bug-fixes and we would like to make sure all of our supported customers have access to these improvements.

The update contains the following package updates:

   * openvswitch 2.12.3

[Test Case]
The following SRU process was followed:
https://wiki.ubuntu.com/OpenStackUpdates

In order to avoid regression of existing consumers, the OpenStack team will run their continuous integration test against the packages that are in -proposed. A successful run of all available tests will be required before the proposed packages can be let into -updates.

The OpenStack team will be in charge of attaching the output summary of the executed tests. The OpenStack team members will not mark ‘verification-done’ until this has happened.

[Regression Potential]
In order to mitigate the regression potential, the results of the
aforementioned tests are attached to this bug.