Updated Ceilometer driver as per new datasource driver

Ceilometer driver now uses Translators commonly refactored in datasource
driver.
Also updated the test code to test the ceilometer driver.
Added call to register_translator().

Fixes bug: 1388967

Change-Id: I2913c1b9cda36548ee38fb90e15a355c1226f38f
Merge "Updated Ceilometer driver as per new datasource driver"