Make (graphite|gdash).wm.o go through misc-eqiad-lb

The service checks for graphite.wikimedia.org and gdash.wikimedia.org uses
HTTPS, but tungsten doesn't serve HTTPS requests -- it gets free SSL
termination from misc-eqiad. We could convert the check to a 'check_http'
instead, but it is better to have the check actually go through the load
balancer. That way, the check really does check that the site is up.

Also sets the 'host' arg for the 5xx check to $::realm, so that tungsten isn't
cited in alerts that have nothing to do with it.

Change-Id: If4e8f3f17374d4b994f7f04e3f96d49e51eb6e88
Merge "Make (graphite|gdash).wm.o go through misc-eqiad-lb" into production