test target: launch user sshd for opening term

- fixtures for user ssh server (authorized_keys, ssh, sshd_config,
ssh_host_rsa_key, ssh.pub)
- exec following cmd
$ /usr/bin/sshd
    - D
    -f sshd_config
    -h ssh_host_rsa_key
    -o AuthorizedKeysFile=authorized_keys
    -p port
- uncomment former terminal tests for open/close

Change-Id: If1765c4860ef3a95f7a92f1f9652427828b98083
Signed-off-by: Clément Bénier <clement.benier@iot.bzh>