HP 3PAR manage_existing with volume-type support

Make manage_existing() modify and tune the volume based
on the volume-type.  Leverages retype() code.

Partially Implements: blueprint add-export-import-volumes

Change-Id: I2923596a6f2299788a7182fb86a5dfc897436302
Merge "HP 3PAR manage_existing with volume-type support"