Add metadata_areas_ignored list and functions to manage ignored mdas.

Add metadata_areas_ignored list and functions to manage ignored mdas.

Add a second mda list, metadata_areas_ignored to fid, and a couple
functions, fid_add_mda() and fid_add_mdas() to help manage the lists.

These functions are needed to properly count the ignored mdas and
manage the lists attached to the 'fid' and ultimately the 'vg'.

Ensure metadata_areas_ignored is initialized in other formats, even
if the list is never used.

Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>