This is related to HELP ticket. This task is not exactly reproducing the problem, and may not help to resolve this ticket, however by itself it reproduces an important failure scenario. If we are lucky, it can uncover some problem related to HELP-22913 even though it's not the same failure.

The idea is to make the primary invisible to mongos for some time, and then do the failover. We need to verify that mongos is capable to detect that primary is not functional and make the RSM to detect the new primary.