[lvm] Add information about metadata areas to the command "pvs".

When investigating LVM issues it can be very useful to have information
about mda copies and size. This patch adds the following columns to
the output of the existing 'pvs -a -v' command:

pv_mda_free,pv_mda_size,pv_mda_count,pv_mda_used_count

Signed-off-by: Jose Castillo <jcastillo@redhat.com>