Support stunnel for protecting livestatus queries

[ganto]

In a distributed multisite setup the Check_MK master site will query the status of the service checks run by the slave site via plain text TCP (by default on port 6557) which is provided by livestatus (also see #33). This connection is unencrypted and unauthenticated which might not satisfy everyone's security policies, especially when being run cross-datacenter.

Add some minimal protection by wrapping the connection into stunnel leveraging debops.stunnel.