Enumerate Instance Names of the class (and subclasses) defined by op.
Arguments are the client object pointer cl, an ObjectPath object pointer op with the reference that contains namespace and classname compo-
nents, and rc which returns the operation status (suppressed when NULL).
When successful the CMCIClientFT.enumInstanceNames() function returns a pointer to a CMPIEnumeration object that contains strings for each
instance name found for the class and sets a successful operation status code in rc. When unsuccessful it returns a NULL pointer and sets
the operation status error code and corresponding error string in rc.