Small performance improvement starting command sequence

Author: dougwilson

Changes.md

@@ -4,6 +4,10 @@ This file is a manually maintained list of changes for each release. Feel free
 to add your changes here when sending pull requests. Also send corrections if
 you spot any mistakes.
 
+## HEAD
+
+* Small performance improvement starting command sequence
+
 ## v2.16.0 (2018-07-17)
 
 * Add Amazon RDS GovCloud SSL certificates #1876

lib/protocol/Protocol.js

@@ -167,8 +167,10 @@ Protocol.prototype._enqueue = function(sequence) {
       err.timeout = sequence._timeout;
 
       self._delegateError(err, sequence);
-    })
-    .on('start-tls', function() {
+    });
+
+  if (sequence.constructor === Sequences.Handshake) {
+    sequence.on('start-tls', function () {
       sequence._timer.active();
       self._connection._startTLS(function(err) {
         if (err) {
@@ -183,6 +185,7 @@ Protocol.prototype._enqueue = function(sequence) {
         sequence._tlsUpgradeCompleteHandler();
       });
     });
+  }
 
   if (this._queue.length === 1) {
     this._parser.resetPacketNumber();