This task is meant to track the efforts to deploy https://gerrit.wikimedia.org/r/#/c/operations/puppet/+/492948/
Mcrouter currently blocks when set/deletes are replicated to codfw until it receives a confirmation from both dcs (memcached in eqiad, mcrouter proxy in codfw). This causes extra latencies that could be avoided, as explained in the correspondence of the above code change.
The plan would be to roll out the change for some mw1* hosts (rather than all of them) to observe/test its behavior, and slowly roll it out everywhere.