API: properly handle invalid JSON to return a 400 status
The API did not treat invalid JSON payloads as a 400 error, as a result
returning a 500 error;
Before this change, an invalid JSON body would return a 500 error;
```bash
curl -v \
--unix-socket /var/run/docker.sock \
-X POST \
"http://localhost/v1.30/networks/create" \
-H "Content-Type: application/json" \
-d '{invalid json'
```
```
> POST /v1.30/networks/create HTTP/1.1
> Host: localhost
> User-Agent: curl/7.52.1
> Accept: */*
> Content-Type: application/json
> Content-Length: 13
>
* upload completely sent off: 13 out of 13 bytes
< HTTP/1.1 500 Internal Server Error
< Api-Version: 1.40
< Content-Type: application/json
< Docker-Experimental: false
< Ostype: linux
< Server: Docker/dev (linux)
< Date: Mon, 05 Nov 2018 11:55:20 GMT
< Content-Length: 79
<
{"message":"invalid character 'i' looking for beginning of object key string"}
```
Empty request:
```bash
curl -v \
--unix-socket /var/run/docker.sock \
-X POST \
"http://localhost/v1.30/networks/create" \
-H "Content-Type: application/json"
```
```
> POST /v1.30/networks/create HTTP/1.1
> Host: localhost
> User-Agent: curl/7.54.0
> Accept: */*
> Content-Type: application/json
>
< HTTP/1.1 500 Internal Server Error
< Api-Version: 1.38
< Content-Length: 18
< Content-Type: application/json
< Date: Mon, 05 Nov 2018 12:00:18 GMT
< Docker-Experimental: true
< Ostype: linux
< Server: Docker/18.06.1-ce (linux)
<
{"message":"EOF"}
```
After this change, a 400 is returned;
```bash
curl -v \
--unix-socket /var/run/docker.sock \
-X POST \
"http://localhost/v1.30/networks/create" \
-H "Content-Type: application/json" \
-d '{invalid json'
```
```
> POST /v1.30/networks/create HTTP/1.1
> Host: localhost
> User-Agent: curl/7.52.1
> Accept: */*
> Content-Type: application/json
> Content-Length: 13
>
* upload completely sent off: 13 out of 13 bytes
< HTTP/1.1 400 Bad Request
< Api-Version: 1.40
< Content-Type: application/json
< Docker-Experimental: false
< Ostype: linux
< Server: Docker/dev (linux)
< Date: Mon, 05 Nov 2018 11:57:15 GMT
< Content-Length: 79
<
{"message":"invalid character 'i' looking for beginning of object key string"}
```
Empty request:
```bash
curl -v \
--unix-socket /var/run/docker.sock \
-X POST \
"http://localhost/v1.30/networks/create" \
-H "Content-Type: application/json"
```
```
> POST /v1.30/networks/create HTTP/1.1
> Host: localhost
> User-Agent: curl/7.52.1
> Accept: */*
> Content-Type: application/json
>
< HTTP/1.1 400 Bad Request
< Api-Version: 1.40
< Content-Type: application/json
< Docker-Experimental: false
< Ostype: linux
< Server: Docker/dev (linux)
< Date: Mon, 05 Nov 2018 11:59:22 GMT
< Content-Length: 49
<
{"message":"got EOF while reading request body"}
```
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
c7b488fbc8