Feature Request: VReplication: add force flag for SwitchTraffic and ReverseTraffic

[mattlord]

Feature Description

There are some errors which could be encountered when performing a traffic switch that, in certain urgent situations, could be considered non-fatal when explicitly instructed with a --force flag.

Use Case(s)

An example is when having done a SwitchTraffic you realize there's a major problem — potentially causing a major outage — but you cannot ReverseTraffic because one tablet is down or otherwise not responding which causes the tablet refresh to fail. In this case a force flag would be very desirable.