LDAP Auth running even if server disabled

Problem/Motivation

I have a site configuration where I need to be able to login with user credentials from drupal base without the ldap auth running if I have my LDAP server disabled in DEV environment. The LDAP is protected via VPN, so because of that I only need it running on production. This works well on production because the LDAP is available and system has no problem with binding the server.

Debug Report

Use case:
1. Administrator creates the user by entering the users' CN from the LDAP AD;
2. The user is created and associated to the drupal base system if it is available in the LDAP;
3. User logs in using the credentials that are either set in drupal base or using its' credentials from the LDAP
4. While logging in, using LDAP Authentication module, the auth mode is set to "Mixed mode".
5. Evene when entering the correct password credential, it takes too long to log in the user because the LDAP server is unavailable on DEV, therefore, no need to try and authenticate.

Proposed resolution

Disable the LDAP authentication on user login if the server is disabled on site.