Locates a vdata in a vgroup given a list of field names.
Return value
Returns the reference number of the vdata if successful and FAIL (or -1) otherwise.
Description
Vflocate searches the vgroup identified by the parameter vgroup_id for a vdata that contains all of the fields listed in the parameter field_name_list. If that vdata is found, Vflocate will return its reference number.