make the port mapping deprecation error message more obvious see 4075

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@home.org.au> (github: SvenDowideit)
Update daemon docs for exec drivers
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
libcontainer: Use pivot_root instead of chroot

Instead of keeping all the old mounts in the container namespace and
just using subtree as root we pivot_root so that the actual root in
the namespace is the root we want, and then we unmount the previous
mounts.

This has multiple advantages:

* The namespace mount tree is smaller (in the kernel)
* If you break out of the chroot you could previously access the host
  filesystem. Now the host filesystem is fully invisible to the namespace.
* We get rid of all unrelated mounts from the parent namespace, which means
  we don't hog these. This is important if we later switch to MS_PRIVATE instead
  of MS_SLAVE as otherwise these mounts would be impossible to unmount from the
  parent namespace.

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
Merge pull request #4438 from crosbymichael/update-docs

Update daemon docs for exec drivers
Add find tests and remove panic in DEBUG
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Merge pull request #4418 from SvenDowideit/mention-expose-in-port-mapping-deprecation

make the port mapping deprecation error message more obvious
Merge pull request #4448 from alexlarsson/pivot_root

libcontainer: Use pivot_root instead of chroot
Merge pull request #4452 from crosbymichael/small-fixes-to-libcontainer

Add find tests and remove panic in DEBUG
Change veth prefix back to veth

Fixes #4453
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Merge pull request #4456 from crosbymichael/change-veth-name

Change veth prefix back to veth
Remove loopback mount bind

Docker-DCO-1.1-Signed-off-by: Guillaume J. Charmes <guillaume.charmes@docker.com> (github: creack)
remove /run mountpoint

Docker-DCO-1.1-Signed-off-by: Guillaume J. Charmes <guillaume.charmes@docker.com> (github: creack)
Remove /dev tmpfs mountpoint

Docker-DCO-1.1-Signed-off-by: Guillaume J. Charmes <guillaume.charmes@docker.com> (github: creack)
Merge pull request #4457 from creack/remove_loopback_mount

Remove loopback mount
Add shm size cap to mount
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Merge pull request #4460 from crosbymichael/add-shm-size

Add shm size cap to mount
bump open files and procs limit via unitfile

Docker-DCO-1.1-Signed-off-by: Lokesh Mandvekar <lsm5@redhat.com> (github: lsm5)

	modified:   contrib/init/systemd/docker.service
	modified:   contrib/init/systemd/socket-activation/docker.service
Merge pull request #4455 from lsm5/systemd

Bump container limit via systemd conf file