New NO_AUTO_CREATE_USER default breaks grants in MariaDB 10.1

From BOA's MariaDB 10.1 (optional) support + 10.0 used by default:

There are some important changes in MariaDB 10.1 which are not compatible with Aegir (Provision).

Namely, as listed in Upgrading from MariaDB 10.0 to 10.1, MariaDB 10.1 enforces sql_mode and sets default values which break the way GRANT is used in Aegir: NO_AUTO_CREATE_USER, NO_ENGINE_SUBSTITUTION

When you check what NO_AUTO_CREATE_USER means, MariaDB docs explain that:

If the NO_AUTO_CREATE_USER SQL_MODE is set, users can only be created with a CREATE USER statement. In this case GRANT will produce an error when the specified user does not exist.

BOA overrides this change with:

sql_mode = NO_ENGINE_SUBSTITUTION

But Aegir (vanilla) will have to force this to make it work with 10.1.