Tolerance for modified ceilometer alarm notification

Changes to the ceilometer alarm notification payload are
proposed here:

  https://review.openstack.org/40955
  https://review.openstack.org/41056

i.e. field names in the JSON payload are changed with:

  s/state/current/
  s/alarm/alarm_id/

Tolerance is added to the autoscaling logic for the new
field names.

Change-Id: I19f36d9331b6f28a3195fb5012ea0b9ee274ade3
Merge "Tolerance for modified ceilometer alarm notification"