rpmmd: add checksum to repoconfig

We should always specify a checksum when describing a repository to pull
content from. For now, fedora-30 duplicated the checksum. The idea is
that we can have it in one place at some point.

internal/distro/fedora30/os.go

@@ -40,6 +40,7 @@ func (f *Fedora30) Repositories() []rpmmd.RepoConfig {
 			Id:       "fedora",
 			Name:     "Fedora 30",
 			Metalink: "https://mirrors.fedoraproject.org/metalink?repo=fedora-30&arch=x86_64",
+			Checksum: "sha256:9f596e18f585bee30ac41c11fb11a83ed6b11d5b341c1cb56ca4015d7717cb97",
 		},
 	}
 }