More minor copy edits, typo fix.

Docker-DCO-1.1-Signed-off-by: Fred Lifton <fred.lifton@docker.com> (github: fredfl)
Don't compile nsinit
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Merge pull request #6227 from crosbymichael/fix-test-compile

Don't compile nsinit during tests (it has package main)
Merge pull request #6226 from fredlf/copyedits

More minor copy edits, typo fix.
start containers after all of them are registered

Docker-DCO-1.1-Signed-off-by: Victor Vieux <vieux@docker.com> (github: vieux)
add wait4 after kill

Docker-DCO-1.1-Signed-off-by: Victor Vieux <vieux@docker.com> (github: vieux)
Merge pull request #6228 from vieux/fix_restart_links

Fix restart links
Bump version to v0.12.0

Docker-DCO-1.1-Signed-off-by: Tibor Vass <teabee89@gmail.com> (github: tiborvass)
Merge pull request #6230 from tiborvass/bump_v0.12.0

Bump version to v0.12.0
Change version to 0.12.0-dev

Docker-DCO-1.1-Signed-off-by: Tibor Vass <teabee89@gmail.com> (github: tiborvass)
Merge pull request #6238 from tiborvass/merge_release_v0.12.0

Merge release v0.12.0
Docs: add ApiVersion to /version for remote API 1.12

Docker-DCO-1.1-Signed-off-by: Paul Morie <pmorie@gmail.com> (github: pmorie)
docs/google: fix code blocks

Docker-DCO-1.1-Signed-off-by: Johan Euphrosine <proppy@google.com> (github: proppy)
Mention bugfixes in 0.12 changelog
Update contrib/check-config.sh to check for CGROUP_FREEZER (which is newly required), and to use /proc/mounts for checking if we have a cgroup hierarchy instead of using /proc/$$/mountinfo (which on systemd might not list the cgroup hierarchy)

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Merge pull request #6241 from proppy/fix-google-docs

docs/google: fix code blocks
improve trusted location detection

Docker-DCO-1.1-Signed-off-by: Victor Vieux <vieux@docker.com> (github: vieux)
Merge pull request #6255 from vieux/improve_trusted_detection

improve trusted location detection
utils: add test for TimeoutConn

Docker-DCO-1.1-Signed-off-by: Johan Euphrosine <proppy@google.com> (github: proppy)
Add CAP_KILL to unprivileged containers
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)