client: even cleaner use of Transport

First off, sorry for the noise. This is a cleaner step of #8508

Found more of a root cause of the open file handles.
After more testing I found that the open file descriptors will still
occur for TCP:// connections to the daemon, causing client and/or daemon
to fail.

The issue was instantiating a new http.Transport on _ever_ client
request. So each instance held the prior connection alive, but was only
ever used once.

By moving it out to the initilization of DockerCli, we can now have
reuse of idled connections. Simplifies the garbage overhead of the
client too, though that's not usually a deal.

Signed-off-by: Vincent Batts <vbatts@redhat.com>
Add info on --device flag permissions ':rwm'

Signed-off-by: Sven Dowideit <SvenDowideit@home.org.au>

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@home.org.au> (github: SvenDowideit)
Link directly to the 'latest' release alias

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@docker.com> (github: SvenDowideit)
Move registry search API docs into the registry API document.

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@docker.com> (github: SvenDowideit)
add BytesSize in pkg/units

Signed-off-by: Victor Vieux <vieux@docker.com>
Fix support for --env-file in bash completion

Signed-off-by: Harald Albers <github@albersweb.de>
Replace '%s' in create tests

Docker-DCO-1.1-Signed-off-by: Jessica Frazelle <jess@docker.com> (github: jfrazelle)
Replace '%s' in diff tests

Docker-DCO-1.1-Signed-off-by: Jessica Frazelle <jess@docker.com> (github: jfrazelle)
Replace '%s' in rm tests

Docker-DCO-1.1-Signed-off-by: Jessica Frazelle <jess@docker.com> (github: jfrazelle)
Replace '%s' in run tests

Docker-DCO-1.1-Signed-off-by: Jessica Frazelle <jess@docker.com> (github: jfrazelle)
Replace '%s' in test utils

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

Made it clear signed images is a preview feature and added a little more info about how the feature works.

Docker-DCO-1.1-Signed-off-by: Fred Lifton <fred.lifton@docker.com> (github: fredlf)
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)
Merge pull request #8595 from fredlf/signed-image-doco

Expanded release notes
Fix commit api document

The commit message field should be `comment`, not `m`
https://github.com/docker/docker/blob/master/api/server/server.go#L478

Signed-off-by: Huayi Zhang <irachex@gmail.com>
Fix more missing HOME references

Signed-off-by: Andrew Page <admwiggin@gmail.com>
Merge branch 'release' into merge_release_v1.3.0
Change version to 1.3.0-dev

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>