Add send-data-to-ceilometer support for pxe_ipminative driver

This patch will implement pxe_ipminative driver *get_sensors_data* method to get
sensor data by pyghmi get_sensor_data() method call.

Spec:
https://github.com/openstack/ironic-specs/blob/master/specs/juno/send-data-to-ceilometer.rst

Related patch: https://review.openstack.org/#/c/72538/

Change-Id: I2368e78e39970b7a3cffe3d8cb2dd3fce5056635
Merge "Add send-data-to-ceilometer support for pxe_ipminative driver"