Update docker

Changes:

- https://github.com/docker-library/docker/commit/dc04548: Merge pull request https://github.com/docker-library/docker/pull/177 from tmaczukin/rename-docker-socket-variable
- https://github.com/docker-library/docker/commit/be5681f: Rename DOCKER_SOCKET to dockerSocket and unexport it
- https://github.com/docker-library/docker/commit/8d3471f: Rename variable used for defining used docker.sock file

library/docker

@@ -11,7 +11,7 @@ Directory: 19.03
 
 Tags: 19.03.1-dind, 19.03-dind, 19-dind, stable-dind, test-dind, dind
 Architectures: amd64, arm32v6, arm32v7, arm64v8
-GitCommit: c01ffa41486f70c34f020c769bc5bddf106367ea
+GitCommit: be5681f51834bf437e12a27c34858d5f87fab024
 Directory: 19.03/dind
 
 Tags: 19.03.1-dind-rootless, 19.03-dind-rootless, 19-dind-rootless, stable-dind-rootless, test-dind-rootless, dind-rootless
@@ -31,7 +31,7 @@ Directory: 18.09
 
 Tags: 18.09.8-dind, 18.09-dind, 18-dind
 Architectures: amd64, arm32v6, arm32v7, arm64v8
-GitCommit: c01ffa41486f70c34f020c769bc5bddf106367ea
+GitCommit: be5681f51834bf437e12a27c34858d5f87fab024
 Directory: 18.09/dind
 
 Tags: 18.09.8-git, 18.09-git, 18-git