Allow tags for fabio service registration

[robholland]

Please add a way to configure tags that fabio will set on the service it registers. This will allow us to connect to the admin interface of a specific fabio instance when we have more than one fabio instance in a balancer configuration.

[magiconair]

Like this? Could you test it and let me know whether that works for you?

[robholland]

Yeah, I'll give that a test, cheers!

[magiconair]

Forgot logging.

[robholland]

I didn't check the log output, but the tags are set properly :)

[magiconair]

ok, then I'll merge that one as well.

[magiconair]

merged.