osbuild-worker-executor: job-id in control.json as hostname

This commit adds support to set the hostname to the job-id that
is part of the control.json.

cmd/osbuild-worker-executor/export_test.go

@@ -12,6 +12,14 @@ var (
 	HandleIncludedSources = handleIncludedSources
 )
 
+func MockUnixSethostname(new func([]byte) error) (restore func()) {
+	saved := unixSethostname
+	unixSethostname = new
+	return func() {
+		unixSethostname = saved
+	}
+}
+
 func MockOsbuildBinary(t *testing.T, new string) (restore func()) {
 	t.Helper()