implement docker push -a/--all-tags

[thaJeztah]

fixes #2214

• depends on vendor: bump docker and dependencies a9507c6f76627fdc092edc542d5a7ef4a6df5eec #2242

depends on moby/moby#40302 client.ImagePush(): default to ":latest" instead of "all tags"

The docker push command up until v0.9.1
always pushed all tags of a given image, so docker push foo/bar would push (e.g.)
all of foo/bar:latest, foo:/bar:v1, foo/bar:v1.0.0.

Pushing all tags of an image was not desirable in many case, so docker v0.10.0
enhanced docker push to optionally specify a tag to push (docker push foo/bar:v1)
(see moby/moby#3411 and the pull request that implemented
this: moby/moby#4948).

This behavior exists up until today, and is confusing, because unlike other commands,
docker push does not default to use the :latest tag when omitted, but instead
makes it push "all tags of the image"

For example, in the following situation;

docker images

REPOSITORY          TAG                        IMAGE ID            CREATED             SIZE
thajeztah/myimage   latest                     b534869c81f0        41 hours ago        1.22MB

Running docker push thajeztah/myimage seemingly does the expected behavior (it
pushes thajeztah/myimage:latest to Docker Hub), however, it does not so for the
reason expected (:latest being the default tag), but because :latest happens
to be the only tag present for the thajeztah/myimage image.

If another tag exists for the image:

docker images

REPOSITORY          TAG                        IMAGE ID            CREATED             SIZE
thajeztah/myimage   latest                     b534869c81f0        41 hours ago        1.22MB
thajeztah/myimage   v1.0.0                     b534869c81f0        41 hours ago        1.22MB

Running the same command (docker push thajeztah/myimage) will push both images
to Docker Hub.

Note that the behavior described above is currently not (clearly) documented;
the docker push reference documentation (https://docs.docker.com/engine/reference/commandline/push/)
does not mention that omitting the tag will push all tags

This patch changes the default behavior, and if no tag is specified, :latest is
assumed. To push all tags, a new flag (-a / --all-tags) is added, similar
to the flag that's present on docker pull.

With this change:

• docker push myname/myimage will be the equivalent of docker push myname/myimage:latest
• to push all images, the user needs to set a flag (--all-tags), so docker push --all-tags myname/myimage:latest

- What I did

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[albers]

LGTM

[thaJeztah]

e2e looks to be flaky/broken (don't think due to this PR). I was wondering why some PR's were green, but I noticed the Jenkins jobs were not triggered on all PR's. I opened #2256 and #2257 (but they probably are the same issue)

[thaJeztah]

@silvin-lubecki PTAL - kicked CI, and it's green now 👍

[silvin-lubecki]

LGTM