Ingore "Use import/export shortcut"

We occasionally reexport modules to keep interfaces stable, most prominently
in Ganeti.Objects. To keep the export statement readable it is helpful to
explicitly name all the modules reexported. This lint warning would make this
impossible.

Signed-off-by: Klaus Aehlig <aehlig@google.com>
Reviewed-by: Petr Pudlak <pudlak@google.com>