Fix AodhAlarmTest to use gnocchi

This changes the test to use AodhGnocchiAggregationByMetricsAlarm
and add measures using gnocchi api.

Change-Id: I0b2fe154b93d9882b703e95a0b09f139697ceb9a
Closes-Bug: #1727637
diff --git a/requirements.txt b/requirements.txt
index 83d86fd..098082e 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -6,8 +6,8 @@
 oslo.config>=4.6.0 # Apache-2.0
 oslo.log>=3.30.0 # Apache-2.0
 paramiko>=2.0.0 # LGPLv2.1+
-python-ceilometerclient>=2.5.0 # Apache-2.0
 python-cinderclient>=3.2.0 # Apache-2.0
+gnocchiclient>=3.3.1 # Apache-2.0
 python-heatclient>=1.10.0 # Apache-2.0
 python-neutronclient>=6.3.0 # Apache-2.0
 python-novaclient>=9.1.0 # Apache-2.0