Add two new configuration options, RE: TCP checks

This commit adds two additional configuration items:
```
+      default_config :ssh_sleep, 120
+      default_config :no_ssh_tcp_check, false
```

If `no_ssh_tcp_check` is true, `wait_for_sshd(state[:hostname])` will be skipped after sleeping for `ssh_sleep` seconds (default sleep of 2 minutes). These changes are required until test-kitchen can read complete SSH configurations, including any proxies or other overrides.