add docker server version to /info

Signed-off-by: Zhang Kun <zkazure@gmail.com>
Upstream-commit: 708318b076
Component: cli

components/cli/docs/reference/commandline/info.md

@@ -21,6 +21,7 @@ For example:
     $ docker -D info
     Containers: 14
     Images: 52
+    Engine Version: 1.9.0
     Storage Driver: aufs
      Root Dir: /var/lib/docker/aufs
      Backing Filesystem: extfs

components/cli/man/docker-info.1.md

@@ -33,6 +33,7 @@ Here is a sample output:
     # docker info
     Containers: 14
     Images: 52
+    Engine Version: 1.9.0
     Storage Driver: aufs
      Root Dir: /var/lib/docker/aufs
      Dirs: 80