[Spectrum Virtualize family] Added support to pass cleanrate
parameter in volume-type specs. Cleanrate parameter can now be
passed as an extra spec in volume-type or fetched from cinder.conf.
If these are not provided then it will take the default value.
Implements: blueprint ibm-svf-cleanrate-spec
Change-Id: I0a373cd130420ebe775e05db538868a4d333db1b