The Active Directory documentation [1] says you can use the `hudson.plugins.active_directory.ActiveDirectorySecurityRealm.forceLdaps` system property to force connecting via LDAPS. This is broken.
The following pull request updates the code to use this system property:
https://github.com/jenkinsci/active-directory-plugin/pull/8
It also changes the default LDAPS port from 686 to 636.
[1] https://wiki.jenkins-ci.org/display/JENKINS/Active+Directory+plugin#ActiveDirectoryplugin-SecuringaccesstoActiveDirectoryservers