Description of problem:
-----------------------
Composite alarm uses last value from the evaluation periods, causing false positive alarm transition.

    2016-10-03 08:49:35.884 11794 DEBUG aodh.evaluator [-] evaluating alarm c9891f7b-42ac-40fc-8b30-9631d21d228e _evaluate_alarm /usr/lib/python2.7/site-packages/aodh/evaluator/__init__.py:257              [63/1810]
    2016-10-03 08:49:35.885 11794 DEBUG aodh.evaluator.composite [-] Evaluating composite rule alarm c9891f7b-42ac-40fc-8b30-9631d21d228e ... evaluate /usr/lib/python2.7/site-packages/aodh/evaluator/composite.py:213
    2016-10-03 08:49:35.885 11794 DEBUG aodh.evaluator.composite [-] Evaluating gnocchi_aggregation_by_metrics_threshold rule: {u'evaluation_periods': 3, u'metrics': [u'b6ba3db7-78d5-4e66-a592-d999a2988a91', u'7f16d
    ccc-92e6-43a9-a87e-009f078b9b55'], u'threshold': 6.0, u'granularity': 60, u'aggregation_method': u'mean', u'type': u'gnocchi_aggregation_by_metrics_threshold', u'comparison_operator': u'ge'} evaluate /usr/lib/py
    thon2.7/site-packages/aodh/evaluator/composite.py:45
    2016-10-03 08:49:35.885 11794 DEBUG aodh.evaluator.threshold [-] query stats from 2016-10-03 08:45:35.885525 to 2016-10-03 08:49:35.885525 _bound_duration /usr/lib/python2.7/site-packages/aodh/evaluator/threshol
    d.py:89
    2016-10-03 08:49:36.097 11794 DEBUG aodh.evaluator.gnocchi [-] sanitize stats [] _sanitize /usr/lib/python2.7/site-packages/aodh/evaluator/gnocchi.py:48
    2016-10-03 08:49:36.098 11794 DEBUG aodh.evaluator.gnocchi [-] pruned statistics to 0 _sanitize /usr/lib/python2.7/site-packages/aodh/evaluator/gnocchi.py:52
    2016-10-03 08:49:36.098 11794 DEBUG aodh.evaluator.composite [-] Evaluating gnocchi_aggregation_by_resources_threshold rule: {u'evaluation_periods': 3, u'metric': u'radosgw.api.request', u'threshold': 4.0, u'gra
    nularity': 60, u'aggregation_method': u'mean', u'query': u'{"or":[{"=":{"id":"alarm-resource-3"}},{"=":{"id":"alarm-resource-4"}}]}', u'type': u'gnocchi_aggregation_by_resources_threshold', u'comparison_operator
    ': u'ge', u'resource_type': u'ceph_account'} evaluate /usr/lib/python2.7/site-packages/aodh/evaluator/composite.py:45
    2016-10-03 08:49:36.098 11794 DEBUG aodh.evaluator.threshold [-] query stats from 2016-10-03 08:45:36.098557 to 2016-10-03 08:49:36.098557 _bound_duration /usr/lib/python2.7/site-packages/aodh/evaluator/threshol
    d.py:89
    2016-10-03 08:49:36.598 11794 DEBUG aodh.evaluator.gnocchi [-] sanitize stats [[u'2016-10-03T08:00:00+00:00', 3600.0, 3.1875], [u'2016-10-03T08:45:00+00:00', 900.0, 3.3], [u'2016-10-03T08:45:00+00:00', 300.0, 3$
    3], [u'2016-10-03T08:45:00+00:00', 60.0, 3.0], [u'2016-10-03T08:46:00+00:00', 60.0, 3.0], [u'2016-10-03T08:47:00+00:00', 60.0, 3.0], [u'2016-10-03T08:48:00+00:00', 60.0, 3.5], [u'2016-10-03T08:49:00+00:00', 60.$
    , 4.0]] _sanitize /usr/lib/python2.7/site-packages/aodh/evaluator/gnocchi.py:48
    2016-10-03 08:49:36.599 11794 DEBUG aodh.evaluator.gnocchi [-] pruned statistics to 3 _sanitize /usr/lib/python2.7/site-packages/aodh/evaluator/gnocchi.py:52
    2016-10-03 08:49:36.599 11794 DEBUG aodh.evaluator.threshold [-] comparing value 3.0 against threshold 4.0 _compare /usr/lib/python2.7/site-packages/aodh/evaluator/threshold.py:175
    2016-10-03 08:49:36.600 11794 DEBUG aodh.evaluator.threshold [-] comparing value 3.5 against threshold 4.0 _compare /usr/lib/python2.7/site-packages/aodh/evaluator/threshold.py:175
    2016-10-03 08:49:36.600 11794 DEBUG aodh.evaluator.threshold [-] comparing value 4.0 against threshold 4.0 _compare /usr/lib/python2.7/site-packages/aodh/evaluator/threshold.py:175
    2016-10-03 08:49:36.601 11794 INFO aodh.evaluator [-] alarm c9891f7b-42ac-40fc-8b30-9631d21d228e transitioning to alarm because Composite rule alarm with composition form: (rule1 or rule2) transition to alarm, $
    ue to rules: rule2 outside their threshold.



Version-Release number of selected component (if applicable):
-------------------------------------------------------------
openstack-aodh-evaluator-3.0.0-0.20160907221145.3990c5b.el7ost.noarch
openstack-aodh-notifier-3.0.0-0.20160907221145.3990c5b.el7ost.noarch
openstack-aodh-common-3.0.0-0.20160907221145.3990c5b.el7ost.noarch
puppet-aodh-9.2.0-0.20160902115754.16ea22a.el7ost.noarch
openstack-aodh-listener-3.0.0-0.20160907221145.3990c5b.el7ost.noarch
python-aodhclient-0.6.0-0.20160826150744.65d2e62.el7ost.noarch
openstack-aodh-api-3.0.0-0.20160907221145.3990c5b.el7ost.noarch


How reproducible:
100%

Steps to Reproduce:
1. Create composite alarm
aodh --debug alarm create \
--type composite \
--name Composite-OR-Alarm \
--description 'Composite OR Alarm' \
--severity critical \
--enabled True \
--alarm-action 'log://' \
--ok-action 'log://' \
--insufficient-data-action 'log://' \
--evaluation-periods 3 \
--composite-rule  '{"or": [{"type":"gnocchi_aggregation_by_metrics_threshold","threshold": 6, "metrics":["b6ba3db7-78d5-4e66-a592-d999a2988a91", "7f16dccc-92e6-43a9-a87e-009f078b9b55"], "evaluation_periods": 3, "granularity": 60, "comparison_operator": "ge", "aggregation_method":"mean"}, { "type":"gnocchi_aggregation_by_resources_threshold", "query": "{\"or\":[{\"=\":{\"id\":\"alarm-resource-3\"}},{\"=\":{\"id\":\"alarm-resource-4\"}}]}", "metric": "radosgw.api.request", "evaluation_periods":3, "granularity":60, "comparison_operator": "ge", "threshold":"4", "resource_type":"ceph_account", "aggregation_method":"mean"}]}'

2. Trigger alarm transition

for i in {1..9}
do
     ceilometer sample-create --resource-id alarm-resource-3 --meter-name radosgw.api.request --meter-type gauge --meter-unit unit1 --sample-volume ${i};     
     ceilometer sample-create --resource-id alarm-resource-4 --meter-name radosgw.api.request --meter-type gauge --meter-unit unit1 --sample-volume 5;
     sleep 60; 
done

3. Assert alarm transitions to new state