subtests.docker_cli: Add run_env test

this tests the ENV related features. Currently it only contains one
subsubtest, which is focused on linked containers. It sends data
using the addr from ENV to the server, which resends them back.

In the end it checks the valid data + ENV variables added via `-e x=y`
including the linked values ($linked_ENV_...)

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
subtests.docker_cli.run_env: Add couple of env checks

Check another expected environments:
SERVER_NAME=/$client_name/server
SERVER_PORT=tcp://$addr:$port
SERVER_PORT_$port_TCP=tcp://$addr:$port
SERVER_PORT_$port_TCP_ADDR=$addr
SERVER_PORT_$port_TCP_PORT=$port
SERVER_PORT_$port_TCP_PROTO=tcp

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
Merge pull request #285 from ldoktor/run_env

subtests.docker_cli: Add run_env test