Description:

Users coming from OAuth service get "guest" role thanks to #5842 but seems that since version 1.0.3, "user" role is also added

Steps to reproduce:

1. Configure OAuth service with role mapping
2. Login with OAuth service and a new user
3. The new user has role from OAuth mapping + "user" role

Expected behavior:

Only role from OAuth mapping should stay

Actual behavior:

User has role from OAuth mapping + "user" role

Server Setup Information:

• Version of Rocket.Chat Server: 1.0.3
• Operating System: Debian
• Deployment Method: tar
• Number of Running Instances: 7
• DB Replicaset Oplog: true
• NodeJS Version: 8.12.0
• MongoDB Version: 4.0.7

Additional context

Maybe linked to #13823 ?