Use UserRoleAssociation to get private roles

If I understand this correctly this should work even if the user email
changes.

lib/galaxy/security/__init__.py

@@ -766,7 +766,8 @@ class GalaxyRBACAgent(RBACAgent):
 
     def get_private_user_role(self, user, auto_create=False):
         role = self.sa_session.query(self.model.Role) \
-                              .filter(and_(self.model.Role.table.c.name == user.email,
+                              .filter(and_(self.model.UserRoleAssociation.table.c.user_id == user.id,
+                                           self.model.Role.table.c.id == self.model.UserRoleAssociation.table.c.role_id,
                                            self.model.Role.table.c.type == self.model.Role.types.PRIVATE)) \
                               .first()
         if not role: