We found that the 3.19 Ubuntu kernel has a bug and
the pagemap cache doesn't work properly on this kernel.

Unfortunately Travis-CI allows to create intancies only with this kernel,
so we need to add this workaround.

https://github.com/xemul/criu/issues/207

Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Reviewed-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>