Add client cert api

according to documentation :

shell – Execute shell commands on targets
It is almost exactly like the command module but runs the command through a shell (/bin/sh) on the remote node.

and:

command – Execute commands on targets
The command(s) will not be processed through the shell, so variables like $HOME and operations like "<", ">", "|", ";" and "&" will not work. Use the shell module if you need these features.

cannot reconfigure docker network if python library are not installed.

fix step order

Allow to pass extras arg to swarm init.

ex: customize default-addr-pool

```
docker_swarm_init_extra_options: |
  --default-addr-pool 10.184.32.0/19 \
  --default-addr-pool-mask-length 28
```

swarm init extras options

…bels.yml

Fix: Replace fqdn usage with ansible hostname in tasks/setup-swarm-labels.yml