mlaunch: Use default SASL/SCRAM mechanisms when creating users.

[matthewdale]

Description of changes

There is currently a check that explicitly prevents creating a SCRAM-SHA-256 user credential for newer server versions. Remove that SASL/SCRAM default mechanism override now that all official MongoDB drivers support SASL/SCRAM mechanism SCRAM-SHA-256 (see DRIVERS-439).

Fixes https://github.com/rueckstiess/mtools/issues/879

Testing

1. Create a standalone deployment with auth enabled.

   python3 mtools/mlaunch/mlaunch.py init \
   --dir ~/data/mtools/5.0.0 \
   --single \
   --binarypath $(m bin 5.0.0)  \
   --auth

2. List user info and confirm that credentials for all default SASL/SCRAM mechanisms for MongoDB v5.0.0 are created (SCRAM-SHA-1, SCRAM-SHA-256).

   mongosh "mongodb://user:password@localhost:27017/admin" --quiet --eval "db.system.users.find()"
   [
   {
   _id: 'admin.user',
   userId: UUID("72e25aa8-a058-47a4-b83b-d7c856291511"),
   user: 'user',
   db: 'admin',
   credentials: {
     'SCRAM-SHA-1': {
       iterationCount: 10000,
       salt: <REDACTED>,
       storedKey: <REDACTED>,
       serverKey: <REDACTED>
     },
     'SCRAM-SHA-256': {
       iterationCount: 15000,
       salt: <REDACTED>,
       storedKey: <REDACTED>,
       serverKey: <REDACTED>
     }
   },
   roles: [
     { role: 'dbAdminAnyDatabase', db: 'admin' },
     { role: 'readWriteAnyDatabase', db: 'admin' },
     { role: 'userAdminAnyDatabase', db: 'admin' },
     { role: 'clusterAdmin', db: 'admin' }
   ]
   }
   ]

O/S testing:	O/S	Version(s)
Linux
macOS	12.4
Windows

[stennie]

Thanks @matthewdale !