implement wait on freeze

Docker-DCO-1.1-Signed-off-by: Victor Vieux <vieux@docker.com> (github: vieux)
Merge pull request #6187 from vieux/wait_freeze

Implement wait on freeze
Add ability to pause/unpause containers via cgroups freeze

This patch adds pause/unpause to the command line, api, and drivers
for use on containers.  This is implemented using the cgroups/freeze
utility in libcontainer and lxc freeze/unfreeze.

Co-Authored-By: Eric Windisch <ewindisch@docker.com>
Co-Authored-By: Chris Alfonso <calfonso@redhat.com>
Docker-DCO-1.1-Signed-off-by: Ian Main <imain@redhat.com> (github: imain)
Integrating systemd freeze functionality.

This pulls together #6061 and #6125

Docker-DCO-1.1-Signed-off-by: Chris Alfonso <calfonso@redhat.com> (github: calfonso)
Add stats for memory allocation failure count and instantaneous cpu usage in the usermode and kernelmode.

Docker-DCO-1.1-Signed-off-by: Vishnu Kannan <vishnuk@google.com> (github: vishh)
Merge pull request #6195 from kieslee/master

pass address of metaHeaders to GetenvJson in ImagePush and ImagePull
Merge pull request #6198 from vishh/stats2

Add more stats to libcontainer.
Merge pull request #6178 from calfonso/freezer-pr-integration

Freezer integration to support container pause/unpause
Remove the API container struct and use env

This change touches docker logs, attach, and start -a along with get
exit code in the client.
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Rename nsinit package to namespaces in libcontainer
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Merge pull request #6204 from crosbymichael/no-structs

Remove the API container struct and use env
Merge pull request #6205 from crosbymichael/rename-namespaces

Rename nsinit package to namespaces in libcontainer
Totally remove insert feature
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Adding initial version of C-based nsenter for allowing execin in
libcontainer.

Docker-DCO-1.1-Signed-off-by: Victor Marmol <vmarmol@google.com> (github: vmarmol)
Move env load to nsenter
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Exclude the user namespace for setns
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Merge pull request #1 from crosbymichael/nsenter-path

Move environment loading to nsenter
Merge pull request #6208 from crosbymichael/remove-insert

Totally remove insert feature
Move doc section in Remote API about removing insert from v1.11 to v1.12

Docker-DCO-1.1-Signed-off-by: Tibor Vass <teabee89@gmail.com> (github: tiborvass)
Merge pull request #6210 from tiborvass/fix_doc_remove_insert_remote_api

Move doc section in Remote API about removing insert from v1.11 to v1.12