libfwupd: Actually use the JCat file to select the metadata file
libfwupd: Actually use the JCat file to select the metadata file

This recent regression was caused when porting libfwupd to the async model.

Fixes https://github.com/fwupd/fwupd/issues/2360

fwupd/fwupd,hughsie/fwupd,fwupd/fwupd,hughsie/fwupd,fwupd/fwupd,hughsie/fwupd,fwupd/fwupd,hughsie/fwupd