🎨 adding an error state on host

[lvenier]

Netbox version	Plugin Version	Agent version	Docker API Version
4.*	2.*	0.39.*	*

Actual Behavior

When we add a Host the agent is sending back a "Running" State change to the host as soon as it has been contacted.
If the agent is not funtionnal as per issue SaaShup/netbox-docker-agent#142 this information is not sent back to the host

Desired Behavior

If the agent has no access to the docker unix socket I would return a "Error" state to the host to inform there is a problem.

CHOICES = [
(STATE_CREATED, "Created", "dark"),
(STATE_RUNNING, "Running", "blue"),
(STATE_ERROR, "Error", "red"),
(STATE_DELETED, "Deleted", "blue"),
(STATE_REFRESHING, "Refreshing", "blue"),
]

As a nice to have a journal entry could be added with a message to inform of the issue.