add --releasever=/ to mkimage-yum.sh

I didn't realize the commit required a Docker-DCO so it failed the travis-ci build. So I removed the commit from my forked repo. Now it looks like there is a pull request with no commit. So here it is again:

Needed to add '--releasever=/' flag to run yum groupinstall on Centos7 (didn't try on anything else). This snippet from yum man page explains why:

```
Note: You may also want to use the option --releasever=/ when creating the installroot as otherwise the $releasever value is taken from the rpmdb within the installroot (and thus.  will  be  empty,  before  creation).
```

Docker-DCO-1.1-Signed-off-by: Matt Schurenko <matt.schurenko@gmail.com> (github: mschurenko)
pkg/version: lint and add comments
docker save: Do not save to a terminal.

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
pkg/truncindex: lint and add comments

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
pkg/units: lint

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
pkg/timeutils: lint and add comments

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
registry: lint

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
pkg/graphdb: some linting

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
Fix the bug of tag a existed tag name of a repository.

Signed-off-by: Lei Jitang <leijitang@huawei.com>
Fix support for --env-file in bash completion

Signed-off-by: Harald Albers <github@albersweb.de>
Add logDone for TestBuildAddSingleFileToNonExistDir

Signed-off-by: Alexandr Morozov <lk4d4@docker.com>
Minor fix of tests names

Signed-off-by: Alexandr Morozov <lk4d4@docker.com>
Avoid fallback to SSL protocols < TLS1.0

Signed-off-by: Tibor Vass <teabee89@gmail.com>

Docker-DCO-1.1-Signed-off-by: Daniel, Dao Quang Minh <dqminh89@gmail.com> (github: dqminh)
Docs syntax fix

the flags must come before the container name.
Migrate container GET API tests from integration to integration-cli

An initial start to migration of the API tests from integration to
the integration-cli model.

Docker-DCO-1.1-Signed-off-by: Phil Estes <estesp@linux.vnet.ibm.com>
(github: estesp)
Add failing testcase for single quotes in CMD

Closes #5701

This is due to @SvenDowideit comment at: https://github.com/docker/docker/issues/5701#issuecomment-58133541
where he asked for a testcase showing the error case.

Signed-off-by: Doug Davis <dug@us.ibm.com>
Cleanup errorOut resp in commit test

Docker-DCO-1.1-Signed-off-by: Jessica Frazelle <jess@docker.com> (github: jfrazelle)

Cleanup errorOut resp in commit test

Docker-DCO-1.1-Signed-off-by: Jessica Frazelle <jess@docker.com> (github: jfrazelle)
Cleanup errorOut resp in port test

Docker-DCO-1.1-Signed-off-by: Jessica Frazelle <jess@docker.com> (github: jfrazelle)
Cleanup errorOut resp in export test

Docker-DCO-1.1-Signed-off-by: Jessica Frazelle <jess@docker.com> (github: jfrazelle)
Cleanup errorOut resp in tag test

Docker-DCO-1.1-Signed-off-by: Jessica Frazelle <jess@docker.com> (github: jfrazelle)