support OPTIONS ping to SBCs

lib/tasks/dial.js

@@ -238,10 +238,11 @@ class TaskDial extends Task {
 
   async _attemptCalls(cs) {
     const {req, srf} = cs;
-
+    const {getSBC} = srf;
     const sbcAddress = cs.direction === CallDirection.Inbound ?
       `${req.source_address}:${req.source_port}` :
-      srf.locals.sbcs[0];
+      getSBC();
+    if (!sbcAddress) throw new Error('no SBC found for outbound call');
     const opts = {
       headers: req && req.has('X-CID') ? Object.assign(this.headers, {'X-CID': req.get('X-CID')}) : this.headers,
       proxy: `sip:${sbcAddress}`,