Currently the only allowed protocol to talk to an LDAP server is ldap://. In
some corporate environment the non-secure port is closed, thus forcing SSL to
talk to the LDAP using the ldaps:// protocol.

In the hudson.security.LDAPSecurityRealm class the URL prefix is always
hardcoded to be "ldap://".

public String getLDAPURL()

{ return "ldap://"+server+'/'+Util.fixNull(rootDN); }

This should have another attribute added to the config to determine if it should
connect using SSL. If the user wants to use SSL, they check the checkbox and
the code uses "ldaps://" as the protocol.