Reject shell-unsafe paths in FreeBSD rc.d install

Validate executable and state directory paths before rendering the
rc.d script so crafted values cannot inject shell syntax.

Signed-off-by: Bryan Frimin <bryan@probo.com>

pkg/deviceagent/service/service_freebsd.go

@@ -59,6 +59,10 @@ func Install(cfg Config) error {
 		return errors.New("state directory is required")
 	}
 
+	if err := validateServicePaths(cfg); err != nil {
+		return err
+	}
+
 	rcTmpl, err := template.New("rc").Parse(rcScriptTmpl)
 	if err != nil {
 		return fmt.Errorf("cannot parse rc.d template: %w", err)