Blocked bp_rules smart notifs on host downtime

This patch adds a missing feature in smart notifications: when a
business rule had services in non ok state, but the host was under
scheduled downtime, a notification was risen. With it, services wich
host is under scheduled downtime won't alert anymore.
Merge pull request #1098 from geektophe/bp_rule_smart_notif_hst_downtime

FIX: Adds bp_rules service smart notifcations blocking on host downtime