health: Don't count hypervisors if no affinity is enforced

If no affinity-hosts is enforced, we shall not fail because the number
of expected HV isn't match.
health: Adding command line options & help

Let's add an inline help but also provide a new command line options.

-f selects the input file
-t allow people defining a title

This title could be used in multiplotting and provides a wait to report
a particular context like a setup change or a plateform name.