Handle EBUSY on remount

Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Merge pull request #6098 from crosbymichael/retry-mount

Handle EBUSY on remount
Adding User Guide

* Added User Guide section outlines.
* Added User Guide to menu.
* Moved HTTPS example to articles.
* Replaced Hello World example with User Guide.
* Moved use cases out of examples.
* Updated Introduction to add User Guide.
* Redirected migrated /use and /articles links.
* Added Docker.io section
* Added Dockerized section
* Added Using Docker section
* Added Docker Images section
* Added Docker Links section
* Added Docker Volumes section

Docker-DCO-1.1-Signed-off-by: James Turnbull <james@lovedthanlost.net> (github: jamtur01)