Move computation of samples to the Ceilometer side

Samples are computed in the Ceiloemter arithmetic transformer,
no need for hacky computation on the UI side now.

Generate the correct test data using this patch:
https://review.openstack.org/#/c/109947/

Or get correct real data using this patch:
https://review.openstack.org/#/c/112245/

Change-Id: I2a6b1190ae2a46e197bc375a415a1f09fac22dab
Merge "Move computation of samples to the Ceilometer side"