Destroy all connections on process exit once pools are drained.

lib/dialects/abstract/connection-manager.js

@@ -44,8 +44,12 @@ ConnectionManager = function(dialect, sequelize) {
 };
 
 ConnectionManager.prototype.onProcessExit = function() {
+  var self = this
+
   if (this.pool) {
-    this.pool.drain();
+    this.pool.drain(function() {
+      self.pool.destroyAllNow();
+    });
   }
 };
 
@@ -116,9 +120,10 @@ ConnectionManager.prototype.initPools = function () {
       destroy: function(connection) {
         return self.pool[connection.queryType].destroy(connection);
       },
-      drain: function() {
-        self.pool.read.drain();
-        self.pool.write.drain();
+      drain: function(cb) {
+        self.pool.write.drain(function() {
+          self.pool.read.drain(cb);
+        });
       },
       read: Pooling.Pool({
         name: 'sequelize-connection-read',