Updated the COPY directive reference: Source can't be a URL for COPY (+ formatting error fixes)

Signed-off-by: Roman Dudin <katrmr@gmail.com>
execdriver/lxc: add comment to MAINTAINERS

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
Add some details about the lifecycle of commands started with docker exec

Signed-off-by: Sven Dowideit <SvenDowideit@home.org.au>
pkg/archive: add interface for Untar

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
Cleanup some integration-cli output

I noticed a few things that were bugging me in the output
of the integration-cli tests.
- one of the tests used println to stdout so we had garage sent to the screen
- some of the test, in their final log message, didn't include the name of
  the group/file e.g.  daemon - run,iptables   was just   run,iptables

And yes, I noticed this because I'm anal :-)  but also because we should keep
the output of the tests as clean as possible so its easy to spot it when
things go bad.

Signed-off-by: Doug Davis <dug@us.ibm.com>
Merge pull request #9091 from duglin/CleanupIntTests

Cleanup some integration-cli output
Merge pull request #9082 from SvenDowideit/pr_out_add_some_details_about_the_lifecycle_of_commands_started_with_docker_exec

Add some details about the lifecycle of commands started with docker exec
Merge pull request #8840 from decadent/fix-da-copy-directive-reference

Nuh uh... quoth the build log: Source can't be a URL for COPY
Merge pull request #9090 from unclejack/archive_interface

pkg/archive: add interface for Untar
registry: add tests for IsSecure

Signed-off-by: Johan Euphrosine <proppy@google.com>
Merge pull request #9095 from proppy/is-secure-test

registry: add tests for IsSecure
Merge pull request #9041 from unclejack/lxc_maintainers_comment

execdriver/lxc: add comment to MAINTAINERS