Change OomKillDisable to be pointer

It's like `MemorySwappiness`, the default value has specific
meaning (default false means enable oom kill).

We need to change it to pointer so we can update it after
container is created.

Signed-off-by: Qiang Huang <h.huangqiang@huawei.com>
(cherry picked from commit 9c2ea42329179c589f5a8991ccf0253eb10fc897)

Conflicts:
	vendor/src/github.com/docker/engine-api/types/container/host_config.go