LDAP user name mapping should be case insensitive RFC2251

Background
LDAP authentication login user name is case insensitive. For example, user account "USER1" and "user1" should point to the same LDAP account and allow log in

Problem
CouchBaser server LDAP Auth Setup is case sensitive. When Couchbase Administrator map LDAP user "UsEr1" within LDAP Auth page, user required to type in user name as "UsEr1" for proper LDAP authentication. This is not an expected behavior.

Request
Update LDAP user name mapping to be case insensitive

RFC 2251 - Lightweight Directory Access Protocol (v3) http://www.faqs.org/rfcs/rfc2251.html

Test scenario
1. Add user name "cbuser1" under LDAP account access page

• user enter cbuser1 + AD password -> login success
• user enter CBuser1 + AD password -> login fail

2, Add user name "CBuser1" and "cbuser1" under LDAP account access page

• user enter CBuser1 + AD password -> login success
• user enter cbuser1 + AD password -> login success