Fix duplicated user in alarms history

Step.Database/Controllers/UsersController.cs

@@ -166,9 +166,13 @@ namespace Step.Database.Controllers
                 var tmpUser = dbCtx
                     .Users
                     .Where(x => x.Deleted == false) // Get not deleted users
-                    .Join(dbCtx.MachinesUsers,u=>u.UserId,m=>m.UserId, (u, m) => new { Users = u, MachinesUsers = m })
+                    .Join( dbCtx.MachinesUsers,
+                        u => u.UserId,
+                        m => m.UserId, 
+                        (u, m) => new { Users = u, MachinesUsers = m }
+                     )
                     .Where(x => x.MachinesUsers.Role.Level < MIN_CMS_ROLE)
-                    .ToList();
+                    .ToList();  
 
                 return tmpUser
                     .Select(x => new DTOMessageUserModel() // Return DTOUserModel
@@ -178,6 +182,7 @@ namespace Step.Database.Controllers
                         LastName = x.Users.LastName,
                         Username = x.Users.Username
                     })
+                    .GroupBy(elem => elem.Id).Select(group => group.First())
                     .ToList();
             }        
         }