CLOUDSTACK-4746:

From functionality point of view following will be changes.
-> Threshold will not be applied for vms undergoing HA process (say during host going down event).
-> Threshold will not be applied for vms undergoing maintenance.
-> Threshold will apply for stop-start vm "after" the skip.counting.hours
(time till which we reserve the capacity for the stopped vm).
Reason being stop-start is a user initiated action and we are giving a time
window  (skip.counting.hours) till which its guaranteed to start in the same
cluster.
After that time, threshold check applies bcz we still want to reserve the
capacity for urgent situations like HA, putting host into maintenance rather than get it consumed in such user
initiated actions.

Signed off by : nitin mehta<nitin.mehta@citrix.com>