VG: fix a typo in the size of the metadata buffer calculation

The typo caused the length to be 0.

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
mlvm: display metadata in json format

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
Silence debug output by default, 'mlvm' re-enables via --debug

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
Tidy up debug printing

Signed-off-by: David Scott <dave.scott@eu.citrix.com>