[19.03 backport] Fix error handling of incorrect --platform values

[thaJeztah]

backport of moby#39527

Relates to docker/docker-py#2382 (comment)

errdefs: convert containerd errors to the correct status code

In situations where the containerd error is consumed directly
and not received over gRPC, errors were not translated.

Add regression tests for invalid platform status codes

Before we handled containerd errors, using an invalid platform produced a 500 status:

curl -v \
-X POST \
--unix-socket /var/run/docker.sock \
"http://localhost:2375/v1.40/images/create?fromImage=hello-world&platform=foobar&tag=latest" \
-H "Content-Type: application/json"

* Connected to localhost (docker.sock) port 80 (#0)
> POST /v1.40/images/create?fromImage=hello-world&platform=foobar&tag=latest HTTP/1.1
> Host: localhost:2375
> User-Agent: curl/7.54.0
> Accept: */*
> Content-Type: application/json
>
< HTTP/1.1 500 Internal Server Error
< Api-Version: 1.40
< Content-Length: 85
< Content-Type: application/json
< Date: Mon, 15 Jul 2019 15:25:44 GMT
< Docker-Experimental: true
< Ostype: linux
< Server: Docker/19.03.0-rc2 (linux)
<
{"message":"\"foobar\": unknown operating system or architecture: invalid argument"}

That problem is now fixed, and the API correctly returns a 4xx status:

curl -v \
-X POST \
--unix-socket /var/run/docker.sock \
"http://localhost:2375/v1.40/images/create?fromImage=hello-world&platform=foobar&tag=latest" \
-H "Content-Type: application/json"

* Connected to localhost (/var/run/docker.sock) port 80 (#0)
> POST /v1.40/images/create?fromImage=hello-world&platform=foobar&tag=latest HTTP/1.1
> Host: localhost:2375
> User-Agent: curl/7.52.1
> Accept: */*
> Content-Type: application/json
>
< HTTP/1.1 400 Bad Request
< Api-Version: 1.41
< Content-Type: application/json
< Docker-Experimental: true
< Ostype: linux
< Server: Docker/dev (linux)
< Date: Mon, 15 Jul 2019 15:13:42 GMT
< Content-Length: 85
<
{"message":"\"foobar\": unknown operating system or architecture: invalid argument"}
* Curl_http_done: called premature == 0

This patch adds tests to validate the behaviour

- How to verify it

make \
  DOCKER_GRAPHDRIVER=vfs \
  TESTDIRS='github.com/docker/docker/integration/image' \
  TESTFLAGS='-test.run ^TestImagePullPlatformInvalid$' \
  binary test-integration


make \
  DOCKER_GRAPHDRIVER=vfs \
  TESTDIRS='github.com/docker/docker/integration/build' \
  TESTFLAGS='-test.run ^TestBuildPlatformInvalid$' \
  binary test-integration

- Description for the changelog

* Fix `POST /images/create` returning a 500 status code when providing an incorrect platform option
* Fix `POST /build` returning a 500 status code when providing an incorrect platform option

[kolyshkin]

LGTM

[andrewhsu]

LGTM