Added default fallback to http1.1 when server doesn't support alpn (s…

…ee: Jetty)

lib/autohttp/agent.js

@@ -136,13 +136,7 @@ class AutoHttp2Agent extends EventEmitter {
     socket.once('secureConnect', () => {
       socket.removeListener('error', socketConnectionErrorHandler)
 
-      const protocol = socket.alpnProtocol
-
-      if (!protocol) {
-        cb(socket.authorizationError)
-        socket.end()
-        return
-      }
+      const protocol = socket.alpnProtocol || 'http/1.1'
 
       if (!supportedProtocols.includes(protocol)) {
         cb(new Error('Unknown protocol' + protocol))