deleteAllFRUVPD API should delete all FRU VPD other than system VPD files

Currently deleteAllFRUVPD API is deleting everything under **/var/lib/phosphor-inventory-manager/xyz/openbmc_project/system/** path, instead API should  remove everything under **/var/lib/phosphor-inventory-manager/xyz/openbmc_project/** other than system VPD files