HP lefthand driver supplies filter_function and goodness_function for scheduler to evaluate

https://blueprints.launchpad.net/cinder/+spec/filtering-weighing-with-driver-supplied-functions has been merged.

As part of the continue effort, we will add the filter_function and goodness_function along with some more stats in the HP lefthand driver. Initial stats in kilo are capacity_utilization and total_volumes of a cluster. The formula of the goodness_function and filter_function are from the cinder.conf. We will not provide default values in the code.

Best practice of openstack cinder lefthand driver will have some information for administrators to set up the goodness_function and filter_function string in the cinder.conf.

There will be more stats later as we identify more useful performance data which will be available after kilo.