domaininfo: Reload periodically

This patch makes chasquid reload domaininfo periodically, so it notices
any external changes made to it.

It is in line with what we do for aliases and authentication already,
and makes it possible for external removals an additions to the
domaininfo database to be picked up without a restart.

internal/testlib/testlib_test.go

@@ -52,3 +52,27 @@ func TestLeaveDirOnError(t *testing.T) {
 	// Remove the directory for real this time.
 	RemoveIfOk(t, dir)
 }
+
+func TestRewriteSafeguard(t *testing.T) {
+	myt := &testing.T{}
+	defer func() {
+		if r := recover(); r != nil {
+			t.Logf("recovered: %v", r)
+		} else {
+			t.Fatalf("check did not panic as expected")
+		}
+	}()
+
+	Rewrite(myt, "/something", "test")
+}
+
+func TestRewrite(t *testing.T) {
+	dir := MustTempDir(t)
+	defer RemoveIfOk(t, dir)
+
+	myt := &testing.T{}
+	Rewrite(myt, dir+"/file", "hola")
+	if myt.Failed() {
+		t.Errorf("basic rewrite failed")
+	}
+}