The following commands do not report WCEs when a no-op - they should wait for write concern in order to know that any previous write that would have made this write a no-op has been majority committed (or committed on whatever number of nodes satisfies the provided wc): * dropAllUsersFromDatabase

• grantPrivilegesToRole 
• grantRolesToRole
• grantRolesToUser
• revokePrivilegesFromRole
• revokeRolesFromRole
• updateRole
• updateUser
   
  The following commands do not report a WCE on error - similar to the no-op case, it's necessary to wait for write concern upon reporting any error that indicates to the user some previous write has been committed on the wc number of nodes. E.g. dropRole should wait before returning RoleNotFound, because it's possible that a previous write dropped the role already, but could be rolled back (if it wasn't wc committed).
• createRole
• createUser
• dropRole
• dropUser
• grantRolesToUser
• updateRole
• updateUser