Replace xxd to cut for google_nvme_id

`google_nvme_id` script currently uses `xxd` to parse nvme device
info, but we need to install additional package `xxd` for fedora,
`vim-common` and `vim-filesystem` for centos (or rhel) before
using it. Replace it with `cut` and we do not need to install
additional packages.
See coreos/fedora-coreos-config#2412 (comment)

src/lib/udev/google_nvme_id

@@ -58,7 +58,7 @@ function err() {
 #######################################
 function get_namespace_device_name() {
   local nvme_json
-  nvme_json="$("$nvme_cli_bin" id-ns -b "$1" | xxd -p -seek 384 | xxd -p -r)"
+  nvme_json="$("$nvme_cli_bin" id-ns -b "$1" | cut -b 384-)"
   if [[ $? -ne 0 ]]; then
     return 1
   fi