migration: Add capability parsing to analyze-migration.py

The script is broken when the configuration/capabilities section is
present. Add support for parsing the capabilities so we can fix it in
the next patch.

Signed-off-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20231009184326.15777-4-farosas@suse.de>