AppData files should be installed in /usr/share/metainfo/
Forwarded from https://bugzilla.gnome.org/show_bug.cgi?id=796946
When building network-manager-vpnc on Debian, lintian complains:
appstream-metadata-in-legacy-location usr/share/appdata/network-manager-vpnc.metainfo.xml
AppStream metadata file was found in /usr/share/appdata/. The AppStream XML files should be placed in /usr/share/metainfo/.
Refer to https://wiki.debian.org/AppStream/Guidelines for details.