Need disable kmem on RHEL in default

[jeffrey4l]

There bugs in kmem in centos 7.x, may be fixed on upcomming 7.8. kmem should be disabled in default now. There is a upstream patch has implemented this, we should backport it now.

• https://bugzilla.redhat.com/show_bug.cgi?id=1507149
• Kernel warning "cache_from_obj: Wrong slab cache." on CentOS 7.4 with overlay2 storage driver moby/moby#35446

[wborn]

We also have this issue with our recent Atomic Host builds causing servers to randomly reboot.

We're testing to see if that patch cherry-picked on top of the docker-1.13.1-rhel branch solves the issue (see these builds). If it does, maybe @mrunalp can help us get it fixed in regular builds?