Fix proc timeout reached error detection

Refs: metarhia/metautil#195
Co-authored-by: Timur Shemsedinov <timur.shemsedinov@gmail.com>
PR-URL: #464

Author: Andrey

lib/server.js

@@ -266,10 +266,10 @@ class Server {
     try {
       result = await proc.invoke(context, args);
     } catch (error) {
-      if (error.message === 'Timeout reached') {
-        error.code = error.httpCode = 408;
-      }
-      return void client.error(error.code, { id, error });
+      let code = error.code === 'ETIMEOUT' ? 408 : 500;
+      if (typeof error.code === 'number') code = error.code;
+      error.httpCode = code;
+      return void client.error(code, { id, error });
     } finally {
       proc.leave();
     }