Fix external link on security of containers

Docker-DCO-1.1-Signed-off-by: Vladimir Rutsky <altsysrq@gmail.com> (github: rutsky)
Merge pull request #4698 from rutsky/external_link_in_rst_fix

Fix external link on security of containers
Add failing test case for issue #4681

Add a failing test case for an issue where docker is not creating a loopback device if networking is dissabled.

Docker-DCO-1.1-Signed-off-by: Timothy Hobbs <timothyhobbs@seznam.cz> (github: https://github.com/timthelion)
Fix issue #4681 - No loopback interface within container when networking is disabled.

Docker-DCO-1.1-Signed-off-by: Timothy Hobbs <timothyhobbs@seznam.cz> (github: https://github.com/timthelion)

Remove loopback code from veth strategy

Docker-DCO-1.1-Signed-off-by: Timothy Hobbs <timothyhobbs@seznam.cz> (github: https://github.com/timthelion)

Looback strategy: Get rid of uneeded code in Create
Docker-DCO-1.1-Signed-off-by: Timothy Hobbs <timothyhobbs@seznam.cz> (github: https://github.com/timthelion)

Use append when building network strategy list

Docker-DCO-1.1-Signed-off-by: Timothy Hobbs <timothyhobbs@seznam.cz> (github: https://github.com/timthelion)

Swap loopback and veth strategies in Networks list

Docker-DCO-1.1-Signed-off-by: Timothy Hobbs <timothyhobbs@seznam.cz> (github: https://github.com/timthelion)

Revert "Swap loopback and veth strategies in Networks list"

This reverts commit 3b8b2c8454171d79bed5e9a80165172617e92fc7.

Docker-DCO-1.1-Signed-off-by: Timothy Hobbs <timothyhobbs@seznam.cz> (github: https://github.com/timthelion)

When initializing networks, only return from the loop if there is an error

Docker-DCO-1.1-Signed-off-by: Timothy Hobbs <timothyhobbs@seznam.cz> (github: https://github.com/timthelion)
Refactor out interface specific information from execdriver.Network

Docker-DCO-1.1-Signed-off-by: Timothy Hobbs <timothyhobbs@seznam.cz> (github: https://github.com/timthelion)