Update API version to v1.40

[thaJeztah]

Some features were merged after API v1.39 shipped as part of the Docker 18.09 betas; this PR updates the API version to 1.40, and corrects the minimal API version for those features.

• Move support for sysctl options in services to API v1.40 - This feature was added in 14da20f (Add support for sysctl options in services #37701), which was merged after API v1.39 shipped as part of the Docker 18.09
• Move support for filtering on node labels to API v1.40 - This feature was added in 514ce73 (Add support for filtering on node labels #37650), which was merged after API v1.39 shipped as part of the Docker 18.09

- Description for the changelog

+ Update API version to 1.40 [moby/moby#38089](https://github.com/moby/moby/pull/38089)

- A picture of a cute animal (not mandatory but encouraged)

image: "Cute Owl by HELMUTTT"

[thaJeztah]

ping @AkihiroSuda (sorry, this will conflict with #38003) @vdemeester

[vdemeester]

LGTM 🐯

[thaJeztah]

Windows RS5 seems to be really broken;

14:05:08 INFO: Docker images of the daemon under test
14:05:08 
14:05:08 REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
14:05:08 
14:05:08 INFO: Base image for tests is microsoft/windowsservercore
14:05:08 INFO: Loading windowsservercore .tar from disk into the daemon under test. This may take some time...
14:06:50 
14:06:50 
14:06:50 ERROR: Failed 'ERROR: Failed to load c:\baseimages\windowsservercore.tar into daemon under test' at 10/26/2018 14:06:50
14:06:50 At C:\gopath\src\github.com\docker\docker\hack\ci\windows.ps1:705 char:21
14:06:50 + ...             Throw $("ERROR: Failed to load $readBaseFrom`:\baseimages ...
14:06:50 +                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
14:06:50 

[yongtang]

LGTM

[thaJeztah]

yeah, let's merge; the RS5 issue is definitely not related