client.bind() should not pass an error to the callback function before having tried to connect to all server urls

First, thanks for the great library! Also very cool that multiple server urls are supported now. Regarding this I ran into a problem.

I use the following code:

this.client.bind(
  this.activeDirectoryConfig.username,
  this.activeDirectoryConfig.password,
  (error) => {
    if (error) {
      sharedLogger.error(
        `Error in ActiveDirectoryClient.bindServiceUser() - ${error}`
      );
      reject(error);
    } else {
      resolve();
    }
  }
);

In case the client can not connect to the first server url in the array, the callback is called with an error. Later, when attempting to connect to the second server url, the callback is called again, this time without an error.

In my opinion the callback should not be called with an error before all server urls have been tried. Only if all attempts have failed, an error should be thrown.

[jsumners]

I think this is something we just plain forgot to address in https://github.com/ldapjs/node-ldapjs/pull/658

I am okay with a PR that:

1. Recognizes an array has been passed for the server list
2. In the case of the array list, tries each server until one succeeds or all fail
3. If all fail returns an error like:

{
  message: 'could not connect to any specified servers',
  details: [
    { message: 'cause for server connection failure', serverAddress: 'tried.one.example.com' },
    { message: 'cause for server connection failure', serverAddress: 'tried.two.example.com' }
  ]
}

[gizmodus]

I would only emit one error. This error could be a summary of all failed connection attempts:

“Error: Connection to ldap servers failed: [error of connection attempt to first server], [error of connection attempt to second server] …”