Add the following test cases to check that mongos receives an isMaster reply "immediately" (or "quickly") after a RS topology change. In order to test this, we'll set the maxAwaitTimeMS to much higher than the default (5 mins). This will allow us to assert that mongos receives the isMaster replies because of a topology change rather than maxAwaitTimeMS.

1. Wait for mongos to discover RS primary, then call replSetStepUp on a secondary.
2. Wait for mongos to discover RS primary, then call replSetReconfig causing a secondary to step up. (done by repl_monitor_refresh.js)
3. Wait for mongos to discover RS primary, then kill the primary causing a secondary to step up.
4. Wait for mongos to discover RS primary, then terminate the primary causing a secondary to step up.
5. MongoS should detect a new member added to the set via replSetReconfig. (done in mongos_no_replica_set_refresh.js)
6. MongoS should detect a member was removed from the set via replSetReconfig. (done in repl_monitor_refresh.js and mongos_no_replica_set_refresh.js)
7. MongoS should detect a change in member tags via replSetReconfig (with no step down).