Add GetParentDeathSignal() to pkg/system

Docker-DCO-1.1-Signed-off-by: Bernerd Schaefer <bj.schaefer@gmail.com> (github: bernerdschaefer)
nsinit.Init() restores parent death signal before exec

Docker-DCO-1.1-Signed-off-by: Bernerd Schaefer <bj.schaefer@gmail.com> (github: bernerdschaefer)
nsinit.DefaultCreateCommand sets Pdeathsig to SIGKILL

Docker-DCO-1.1-Signed-off-by: Bernerd Schaefer <bj.schaefer@gmail.com> (github: bernerdschaefer)
Remove Trailing Whitespace in User-Agent

After removed, the User-Agent shows in log like this:

[debug] http.go:160 https://index.docker.io/v1/repositories/busybox/images --
HEADERS: map[User-Agent:[docker/0.11.1-dev go/go1.2.2 git-commit/8887e00-dirty kernel/3.14.3-n1 os/linux arch/amd64]]

The code also moved all validation work into validVersion,
to keep the main logic as clean.

Docker-DCO-1.1-Signed-off-by: Derek <crq@kernel.org> (github: crquan)
gocapability: upstream fix for unsporrted caps

@vmarmol has made the fix upstream for not failing if the capability
being dropped is returned as invalid from the syscall, which is the case
when the capability is not supported on the host.
This is a blocker presently for RHEL6.5 on CAP_SYSLOG. We have patched
around this in our RPM for the time being, but this is the proper fix.

See also https://github.com/dotcloud/docker/pull/5810

Docker-DCO-1.1-Signed-off-by: Vincent Batts <vbatts@redhat.com> (github: vbatts)
integcli: speed up TestBuildSixtySteps

This improves the TestBuildSixtySteps test by switching from busybox to
scratch and simply adding a file.

This lowers the execution time of that test from 20 seconds to 5
seconds.

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
Add readme file for the api directory

See issue #5873

Docker-DCO-1.1-Signed-off-by: Timothy <timothyhobbs@seznam.cz> (github: https://github.com/timthelion)
Add readme file for the archive directory

See issue #5873

Docker-DCO-1.1-Signed-off-by: Timothy <timothyhobbs@seznam.cz> (github: https://github.com/timthelion)
Add readme for daemon directory

See issue #5873

Docker-DCO-1.1-Signed-off-by: Timothy <timothyhobbs@seznam.cz> (github: https://github.com/timthelion)
Add readme for the daemonconfig directory

See Issue #5873

Docker-DCO-1.1-Signed-off-by: Timothy <timothyhobbs@seznam.cz> (github: https://github.com/timthelion)
Add README.md file for sysinit directory

Note, this text is just copied from sysinit.go

See Issue #5873

Docker-DCO-1.1-Signed-off-by: Timothy <timothyhobbs@seznam.cz> (github: https://github.com/timthelion)
Merge pull request #5874 from timthelion/docs-api-readme

Add readme file for the api directory
Merge pull request #5877 from timthelion/docs-daemon-config-readme

Add readme for the daemonconfig directory
Merge pull request #5876 from timthelion/docs-daemon-readme

Add readme for daemon directory
Merge pull request #5871 from unclejack/speed_up_buildsixtysteps

integcli: speed up TestBuildSixtySteps
Merge pull request #5792 from bernerdschaefer/nsinit-supports-pdeathsig

Add PDEATHSIG support to nsinit library
Merge pull request #5875 from timthelion/docs-archive-readme

Add readme file for the archive directory
Merge pull request #5879 from timthelion/docs-sysinit-readme

Add README.md file for sysinit directory
Make /proc writable, but not /proc/sys and /proc/sysrq-trigger

Some applications want to write to /proc. For instance:

docker run -it centos groupadd foo

Gives: groupadd: failure while writing changes to /etc/group

And strace reveals why:

open("/proc/self/task/13/attr/fscreate", O_RDWR) = -1 EROFS (Read-only file system)

I've looked at what other systems do, and systemd-nspawn makes /proc read-write
and /proc/sys readonly, while lxc allows "proc:mixed" which does the same,
plus it makes /proc/sysrq-trigger also readonly.

The later seems like a prudent idea, so we follows lxc proc:mixed.
Additionally we make /proc/irq and /proc/bus, as these seem to let
you control various hardware things.

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
Merge pull request #5869 from vbatts/vbatts-vendor-capabilities

gocapability: upstream fix for unsporrted caps