Support hairpin NAT without going through docker server

Hairpin NAT is currently done by passing through the docker server.  If
two containers on the same box try to access each other through exposed
ports and using the host IP the current iptables rules will not match the
DNAT and thus the traffic goes to 'docker -d'

This change drops the restriction that DNAT traffic must not originate
from docker0.  It should be safe to drop this restriction because the
DOCKER chain is already gated by jumps that check for the destination
address to be a local address.

Docker-DCO-1.1-Signed-off-by: Darren Shepherd <darren.s.shepherd@gmail.com> (github: ibuildthecloud)
Prevent dynamic allocation of previously allocated ports

Docker-DCO-1.1-Signed-off-by: Andy Kipp <andy@rstudio.com> (github: kippandrew)
Better test error message

Docker-DCO-1.1-Signed-off-by: Andy Kipp <andy@rstudio.com> (github: kippandrew)
Be more explicit in finding next port to allocate

Docker-DCO-1.1-Signed-off-by: Andy Kipp <andy@rstudio.com> (github: kippandrew)
Add err checks for port allocator tests

Docker-DCO-1.1-Signed-off-by: Andy Kipp <andy@rstudio.com> (github: kippandrew)
libcontainer/network: add netns strategy

Docker-DCO-1.1-Signed-off-by: Johan Euphrosine <proppy@google.com> (github: proppy)
libcontainer/nsinit/init: move mount namespace after network

Docker-DCO-1.1-Signed-off-by: Johan Euphrosine <proppy@google.com> (github: proppy)
libcontainer: goimports

Docker-DCO-1.1-Signed-off-by: Johan Euphrosine <proppy@google.com> (github: proppy)
libcontainer: remove duplicate imports

Docker-DCO-1.1-Signed-off-by: Johan Euphrosine <proppy@google.com> (github: proppy)
devicemapper: Better/faster shutdown

Right now shutdown is looping over *all* devicemapper
devices and actively deactivating them, this is pretty
slow if you have a lot of non-active containers. We
instead only deactivate the devices that are mounted.

We also do the shutdown unmount using MNT_DETACH which
forces the unmount in the global namespace, even if it
is busy because of some container having it mounted.
This means the device will be freed when that container
exits.

Also, we move the call to waitClose to deactivateDevice
because all callers of any of them call both anyway.

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
Add initial plugin flag to pass lxc and native driver options
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Dont use custom marshaling for caps and namespaces

This also adds an enabled field to the types so that they
can be easily toggled.
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Allow caps to be toggled in native driver with plugin flag
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Add ability to work with individual namespaces
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Merge branch 'nsinit' of https://github.com/proppy/docker into proppy-nsinit

Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Merge branch 'proppy-nsinit' into pluginflag

Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Allow containers to join the net namespace of other conatiners
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Factor out the native driver config options
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Change flag to -o and --opt
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Change syntax to use dots
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)