default options ping interval to 30s, with env override if desired

lib/utils/sbc-pinger.js

@@ -95,7 +95,7 @@ module.exports = (logger) => {
   setInterval(() => {
     const {srf} = require('../..');
     pingProxies(srf);
-  }, 20000);
+  }, process.env.OPTIONS_PING_INTERVAL || 30000);
 
   // initial ping once we are up
   setTimeout(async() => {