use "btrfs inspect-internal dump-super" instead of btrfs-show-super

[hannut]

btrfs-show-super is obsolete

https://btrfs.wiki.kernel.org/index.php/Manpage/btrfs#STANDALONE_TOOLS

blocks to-lvm --join VG1 /dev/sdb1
Traceback (most recent call last):
File "/root/.local/bin/blocks", line 9, in
load_entry_point('blocks', 'console_scripts', 'blocks')()
File "/root/src/blocks/blocks/main.py", line 2012, in script_main
sys.exit(main())
File "/root/src/blocks/blocks/main.py", line 1678, in main
return args.action(args)
File "/root/src/blocks/blocks/main.py", line 1860, in cmd_to_lvm
block_stack.read_superblocks()
File "/root/src/blocks/blocks/main.py", line 1101, in read_superblocks
self.topmost.read_superblock()
File "/root/src/blocks/blocks/main.py", line 861, in read_superblock
stdout=subprocess.PIPE)
File "/usr/lib64/python3.4/subprocess.py", line 856, in init
restore_signals, start_new_session)
File "/usr/lib64/python3.4/subprocess.py", line 1460, in _execute_child
raise child_exception_type(errno_num, err_msg)
FileNotFoundError: [Errno 2] No such file or directory: 'btrfs-show-super'`

lsb_release -a
LSB Version: :core-4.1-amd64:core-4.1-noarch
Distributor ID: CentOS
Description: CentOS Linux release 7.4.1708 (Core)
Release: 7.4.1708
Codename: Core