Unbind clients when closing

Previously no client was unbound (see trentm#3), now
unbinding both without keeping track if they were actually bound as this
seems to be working (and also destroy-method in ldapjs' connection pool
does so).

lib/ldapauth.js

@@ -89,13 +89,12 @@ function LdapAuth(opts) {
 
 
 LdapAuth.prototype.close = function (callback) {
-  if (! this._adminBound) {
-    callback()
-  } else {
-    this._adminClient.unbind(function (err) {
-      callback(err);
-    });
-  }
+  var self = this;
+  // It seems to be OK just to call unbind regardless of if the
+  // client has been bound (e.g. how ldapjs pool destroy does)
+  self._adminClient.unbind(function(err) {
+    self._userClient.unbind(callback);
+  });
 }
 
 
@@ -117,6 +116,7 @@ LdapAuth.prototype._adminBind = function (callback) {
       self.log && self.log.trace('ldap authenticate: bind error: %s', err);
       return callback(err);
     }
+    self._adminBound = true;
     return callback();
   });
 }