MMS requires at least 3 hosts in connection strings

Customer ran into the issue of specifying only 2 nodes in the connection string.
MMS does require at least 3 nodes, otherwise it won't start and the error message is not useful.
The doc should be explicit in saying you need at least 3 nodes in the connection string.

https://mms.mongodb.com/help-hosted/current/tutorial/configure-application-high-availability/