pvck: repair headers and metadata

pvck: repair headers and metadata

To write a new/repaired pv_header and label_header:

  pvck --repairtype pv_header --file <file> <device>

This uses the metadata input file to find the PV UUID,
device size, and data offset.

To write new/repaired metadata text and mda_header:

  pvck --repairtype metadata --file <file> <device>

This requires a good pv_header which points to one or two
metadata areas.  Any metadata areas referenced by the
pv_header are updated with the specified metadata and
a new mda_header. "--settings mda_num=1|2" can be used
to select one mda to repair.

To combine all header and metadata repairs:

  pvck --repair --file <file> <device>

It's best to use a raw metadata file as input, that was
extracted from another PV in the same VG (or from another
metadata area on the same PV.)  pvck will also accept a
metadata backup file, but that will produce metadata that
is not identical to other metadata copies on other PVs
and other areas.  So, when using a backup file, consider
using it to update metadata on all PVs/areas.

To get a raw metadata file to use for the repair, see
pvck --dump metadata|metadata_search.

List all instances of metadata from the metadata area:
  pvck --dump metadata_search <device>

Save one instance of metadata at the given offset to
the specified file (this file can be used for repair):

  pvck --dump metadata_search --file <file>
    --settings "metadata_offset=<off>" <device>