don't pass aodh options to oslo.db engine facade
don't pass aodh options to oslo.db engine facade

oslo.db EngineFacade class only support options defined by oslo.db,
but we also pass options defined by aodh, so oslo.db complains
with a warning message:

NotSupportedWarning: Configuration option(s) ['alarm_connection', \
'alarm_history_time_to_live'] not supported

This patch makes sure only options defined by oslo.db will be sent
to EngineFacade

Change-Id: I4c259f29af1cab60c3aee41a610b12f64ed5f2d5
Closes-Bug: #1516515

openstack/aodh,openstack/aodh