Add support of HA-flow endpoints update.

[dmitrii-beliakov]

This feature introduces an endpoint update for HA-flows: a partial update without paths recalculation. The condition for executing this kind of update is the updating only fields of endpoint that don't affect paths between them:

• port
• inner VLAN
• outer VLAN

• Create new paths in the FSM to bypass resources allocation and de-allocation
• Make sure proper rules are installed
• find out a way to check whether a diverse group ID has changed

closes #5415

[dmitrii-beliakov]

Here are pictures of the new paths in the update FSM workflow. A new path skips old resources de-allocation (because the new are the same as the old):

and resources reverting on error (again, because the new and the old rules are the same):

[dmitrii-beliakov]

For some reason the third picture is missing. I add it again:

[dmitrii-beliakov]

As for the rules: at this point rule manager creates meters to add, which cannot be added, because they are already on the switch. So. apparently these rules could be skipped. However, it is not that straightforward how to implement it. One idea was to pass an additional flag to the rule manager from the build rules action and adjust the rule manager to use that. Probably there is a better way to implement it.
With the diverse group ID: changes in the diverse group ID says that the path might require recalculation and therefore endpoints update cannot be executed. However, database contains the current state and it is not clear whether the data from the update request lead to the diverse group ID change, it is not a part of the request object. There is a need to implement a method that will be invoked when a decision about the endpoints update is made, whether the diverse group ID changes.