Fixed issue with duplicate roles from LDAP sigin (bigbluebutton#1090)

Co-authored-by: Jesus Federico <[email protected]>

app/models/concerns/auth_values.rb

@@ -57,13 +57,14 @@ def auth_image(auth)
   end
 
   def auth_roles(user, auth)
+    auth['info']['roles'] = "Viewer"
     unless auth['info']['roles'].nil?
       roles = auth['info']['roles'].split(',')
 
       role_provider = auth['provider'] == "bn_launcher" ? auth['info']['customer'] : "greenlight"
       roles.each do |role_name|
-        role = Role.where(provider: role_provider, name: role_name).first
-        user.roles << role unless role.nil?
+        role = Role.find_by(provider: role_provider, name: role_name)
+        user.roles << role if !role.nil? && !user.has_role?(role_name)
       end
     end
   end