Update docker versions tested too

- Use 1.11.2 (as it has bugfixes & such)
- Use 1.12.1 (as it's relatively new)

Signed-off-by: Vincent Demeester <[email protected]>

Author: vdemeester

Dockerfile

@@ -14,7 +14,7 @@ RUN go get github.com/aktau/github-release && \
     go get github.com/golang/lint/golint
 
 # Which docker version to test on and what default one to use
-ENV DOCKER_VERSIONS 1.9.1 1.10.3 1.11.0
+ENV DOCKER_VERSIONS 1.9.1 1.10.3 1.11.2 1.12.1
 ENV DEFAULT_DOCKER_VERSION 1.10.3
 
 # Download docker