When a MySQL server is upgraded to 8.0.x versions from versions 5.7 and
below, the table metadata has to be upgraded. The .frm file contents
are read and then installed in DD. But the .frm files don't have any
information about the foreign keys. So during upgrade, the foreign key
information is not installed in the DD.

This patch fixes that by using the foreign key information available in
the NDB to update the DD during table metadata upgrade. Also enabled
and updated the ndb_metadata_upgrade_fk test.

Change-Id: Id9e98538090acb5a82ed47edf3bb6cf10ec57840